The Query Processor is responsible for translating the Metabase Query Language into HoneySQL SQL forms.

(ns metabase.driver.sql.query-processor
  (:require
   [clojure.core.match :refer [match]]
   [clojure.string :as str]
   [honey.sql :as sql]
   [honey.sql.helpers :as sql.helpers]
   [honey.sql.protocols]
   [java-time.api :as t]
   [medley.core :as m]
   [metabase.driver :as driver]
   [metabase.driver.common :as driver.common]
   [metabase.driver.sql.query-processor.deprecated :as sql.qp.deprecated]
   [metabase.legacy-mbql.schema :as mbql.s]
   [metabase.legacy-mbql.util :as mbql.u]
   [metabase.lib.convert :as lib.convert]
   [metabase.lib.metadata :as lib.metadata]
   [metabase.lib.query :as lib.query]
   [metabase.lib.schema.common :as lib.schema.common]
   [metabase.lib.util.match :as lib.util.match]
   [metabase.query-processor.debug :as qp.debug]
   [metabase.query-processor.error-type :as qp.error-type]
   [metabase.query-processor.middleware.annotate :as annotate]
   [metabase.query-processor.middleware.wrap-value-literals :as qp.wrap-value-literals]
   [metabase.query-processor.store :as qp.store]
   [metabase.query-processor.util.add-alias-info :as add]
   [metabase.query-processor.util.nest-query :as nest-query]
   [metabase.query-processor.util.transformations.nest-breakouts :as qp.util.transformations.nest-breakouts]
   [metabase.util :as u]
   [metabase.util.date-2 :as u.date]
   [metabase.util.honey-sql-2 :as h2x]
   [metabase.util.i18n :refer [tru]]
   [metabase.util.log :as log]
   [metabase.util.malli :as mu])
  (:import
   (java.time LocalDate LocalDateTime LocalTime OffsetDateTime OffsetTime ZonedDateTime)
   (java.util UUID)))
(set! *warn-on-reflection* true)

Alias to use for source queries, e.g.:

SELECT source.* FROM ( SELECT * FROM some_table ) source

(def source-query-alias
  "source")

The INNER query currently being processed, for situations where we need to refer back to it.

(def ^:dynamic *inner-query*
  nil)

See [[make-nestable-sql]] but does not wrap in result in parens.

(defn make-nestable-sql*
  [sql]
  (-> sql
      (str/replace #";([\s;]*(--.*\n?)*)*$" "")
      str/trimr
      (as-> trimmed
        ;; Query could potentially end with a comment.
            (if (re-find #"--.*$" trimmed)
              (str trimmed "\n")
              trimmed))))

Do best effort edit to the sql, to make it nestable in subselect.

That requires:

  • Removal of traling comments (after the semicolon).
  • Removing the semicolon(s).
  • Squashing whitespace at the end of the string and replacinig it with newline. This is required in case some comments were preceding semicolon.
  • Wrapping the result in parens.

This implementation does not handle few cases cases properly. 100% correct comment and semicolon removal would probably require parsing sql string and not just a regular expression replacement. Link to the discussion: https://github.com/metabase/metabase/pull/30677

For the limitations see the [[metabase.driver.sql.query-processor-test/make-nestable-sql-test]]

(defn make-nestable-sql
    [sql]
  (str "(" (make-nestable-sql* sql) ")"))
(defn- format-sql-source-query [_clause [sql params]]
  (into [(make-nestable-sql* sql)] params))
(sql/register-clause! ::sql-source-query #'format-sql-source-query :select)

Wrap clause in ::sql-source-query. Does additional validation.

(defn sql-source-query
  [sql params]
  (when-not (string? sql)
    (throw (ex-info (tru "Expected native source query to be a string, got: {0}"
                         (.getCanonicalName (class sql)))
                    {:type  qp.error-type/invalid-query
                     :query sql})))
  (when-not ((some-fn nil? sequential?) params)
    (throw (ex-info (tru "Expected native source query parameters to be sequential, got: {0}"
                         (.getCanonicalName (class params)))
                    {:type  qp.error-type/invalid-query
                     :query params})))
  {::sql-source-query [sql params]})

+----------------------------------------------------------------------------------------------------------------+ | Interface (Multimethods) | +----------------------------------------------------------------------------------------------------------------+

DEPRECATED: Prior to between 0.46.0 and 0.49.0, drivers could use either Honey SQL 1 or Honey SQL 2. In 0.49.0+, all drivers must use Honey SQL 2.

#_{:clj-kondo/ignore [:clojure-lsp/unused-public-var]}
(defmulti honey-sql-version
  {:arglists '(^Long [driver]), :added "0.46.0", :deprecated "0.49.0"}
  driver/dispatch-on-initialized-driver
  :hierarchy #'driver/hierarchy)

Wrap number n in :inline when targeting Honey SQL 2.

(defn inline-num
  {:added "0.46.0"}
  [n]
  {:pre [(number? n)]}
  [:inline n])

Is honeysql-expr a Honey SQL 2 :inline format?

(defn inline?
  {:added "0.46.0"}
  [honeysql-expr]
  (and (vector? honeysql-expr)
       (= (first honeysql-expr) :inline)))

this is the primary way to override behavior for a specific clause or object class.

Cast to integer

(defmulti ->integer
  {:changelog-test/ignore true :added "0.45.0" :arglists '([driver honeysql-expr])}
  driver/dispatch-on-initialized-driver
  :hierarchy #'driver/hierarchy)
(defmethod ->integer :sql
  [_ value]
  (h2x/->integer value))

Cast to float.

(defmulti ->float
  {:changelog-test/ignore true :added "0.45.0" :arglists '([driver honeysql-expr])}
  driver/dispatch-on-initialized-driver
  :hierarchy #'driver/hierarchy)
(defmethod ->float :sql
  [driver value]
  ;; optimization: we don't need to cast a number literal that is already a `Float` or a `Double` to `FLOAT`. Other
  ;; number literals can be converted to doubles in Clojure-land. Note that there is a little bit of a mismatch between
  ;; FLOAT and DOUBLE here, but that's mostly because I'm not 100% sure which drivers have both types. In the future
  ;; maybe we can fix this.
  (cond
    (float? value)
    (h2x/with-database-type-info (inline-num value) "float")

    (number? value)
    (recur driver (double value))

    (inline? value)
    (recur driver (second value))

    :else
    (h2x/cast :float value)))

Return an inline value (as a raw SQL string) for an object x, e.g.

(inline-value :postgres (java-time.api/offset-date-time)) ;; => "timestamp with time zone '2024-07-01 23:35:18.407 +00:00'"

(defmulti ^clojure.lang.MultiFn inline-value
  {:added "0.51.0", :arglists '(^String [driver x])}
  (fn [driver x]
    [(driver/dispatch-on-initialized-driver driver) (class x)])
  :hierarchy #'driver/hierarchy)
(defn- sqlize-value [x]
  (if driver/*driver*
    (inline-value driver/*driver* x)
    (honey.sql.protocols/sqlize x)))

Replace the implentation of [[honey.sql/sqlize-value]] with one that hands off to [[inline-value]] if driver is bound. This way we can have driver-specific inline behavior. Monkey-patching private functions like this is a little questionable for sure but I think it's justified here since there is on other way to consistently guarantee that we hand off to [[sqlize-value]] when compiling something inline.

(alter-var-root #'sql/sqlize-value (constantly sqlize-value))

Return an appropriate HoneySQL form for an object. Dispatches off both driver and either clause name or object class making this easy to override in any places needed for a given driver.

(defmulti ->honeysql
  {:added "0.37.0" :arglists '([driver mbql-expr-or-object])}
  (fn [driver x]
    [(driver/dispatch-on-initialized-driver driver) (mbql.u/dispatch-by-clause-name-or-class x)])
  :hierarchy #'driver/hierarchy)

Wraps a honeysql-expr in an psudeo-MBQL clause that prevents double-compilation if [[->honeysql]] is called on it again.

(defn compiled
  {:added "0.46.0"}
  [honeysql-expr]
  [::compiled honeysql-expr])
(defmethod ->honeysql [:sql ::compiled]
  [_driver [_compiled honeysql-expr :as compiled-form]]
  ;; preserve metadata attached to the compiled form
  (with-meta honeysql-expr (meta compiled-form)))
(defn- format-compiled
  [_compiled [honeysql-expr]]
  (sql/format-expr honeysql-expr {:nested true}))
(sql/register-fn! ::compiled #'format-compiled)

HoneySQL form that should be used to get the current datetime (or equivalent). Defaults to :%now. Should ideally include the database type info on the form (ex: via [[h2x/with-type-info]]).

(defmulti current-datetime-honeysql-form
  {:added "0.34.2" :arglists '([driver])}
  driver/dispatch-on-initialized-driver
  :hierarchy #'driver/hierarchy)
(defmethod current-datetime-honeysql-form :sql
  [_driver]
  :%now)

Return a HoneySQL form for truncating a date or timestamp field or value to a given resolution, or extracting a date component.

honeysql-expr is already compiled to Honey SQL, so DO NOT call [[->honeysql]] on it.

TODO - rename this to temporal-bucket or something that better describes what it actually does

(defmulti date
  {:added "0.32.0" :arglists '([driver unit honeysql-expr])}
  (fn [driver unit _] [(driver/dispatch-on-initialized-driver driver) unit])
  :hierarchy #'driver/hierarchy)

default implementation for :default bucketing returns expression as-is

(defmethod date [:sql :default] [_ _ expr] expr)

We have to roll our own to account for arbitrary start of week

(defmethod date [:sql :second-of-minute] [_driver _ expr] (h2x/second expr))
(defmethod date [:sql :minute-of-hour]   [_driver _ expr] (h2x/minute expr))
(defmethod date [:sql :hour-of-day]      [_driver _ expr] (h2x/hour expr))
(defmethod date [:sql :week-of-year]
  [driver _ expr]
  ;; Some DBs truncate when doing integer division, therefore force float arithmetics
  (->honeysql driver [:ceil (compiled (h2x// (date driver :day-of-year (date driver :week expr)) 7.0))]))
(defmethod date [:sql :month-of-year]    [_driver _ expr] (h2x/month expr))
(defmethod date [:sql :quarter-of-year]  [_driver _ expr] (h2x/quarter expr))
(defmethod date [:sql :year-of-era]      [_driver _ expr] (h2x/year expr))
(defmethod date [:sql :week-of-year-iso] [_driver _ expr] (h2x/week expr))

Returns a HoneySQL form for calculating the datetime-diff for a given unit. This method is used by implementations of ->honeysql for the :datetime-diff clause. It is recommended to implement this if you want to use the default SQL implementation of ->honeysql for the :datetime-diff, which includes validation of argument types across all units.

(defmulti datetime-diff
  {:arglists '([driver unit field-or-value field-or-value]), :added "0.46.0"}
  (fn [driver unit _ _] [(driver/dispatch-on-initialized-driver driver) unit])
  :hierarchy #'driver/hierarchy)

Takes a datetime expession, return a HoneySQL form that calculate how many days from the Jan 1st till the start of first full week.

A full week is a week that contains 7 days in the same year.

Example: Assume start-of-week setting is :monday

(days-till-start-of-first-full-week driver '2000-04-05') -> 2

Because '2000-01-01' is Saturday, and 1st full week starts on Monday(2000-01-03) => 2 days

(defn- days-till-start-of-first-full-week
  [driver honeysql-expr]
  (let [start-of-year                (date driver :year honeysql-expr)
        day-of-week-of-start-of-year (date driver :day-of-week start-of-year)]
    (h2x/- 8 day-of-week-of-start-of-year)))

Calculate the week of year for :us or :instance mode. Returns a Honey SQL expression.

The idea for both modes are quite similar: - 1st Jan is always in the 1st week - the 2nd weeks start on the first start-of-week setting.

The algorithm: week-of-year = 1 partial-week + n full-weeks Where: - partial-week: is the week that starts from 1st Jan, until the next start-of-week - full-weeks: are weeks that has all week-days are in the same year.

Now, all we need to do is to find full-weeks, and it could be computed by this formula: full-weeks = ceil((doy - days-till-start-of-first-full-week) / 7) Where: - doy: is the day of year of the input date - days-till-start-of-first-full-week: is how many days from 1st Jan to the first start-of-week.

(defn- week-of-year
  [driver honeysql-expr mode]
  (let [days-till-start-of-first-full-week (binding [driver.common/*start-of-week*
                                                     (case mode
                                                       :us :sunday
                                                       :instance nil)]
                                             (days-till-start-of-first-full-week driver honeysql-expr))
        total-full-week-days               (h2x/- (date driver :day-of-year honeysql-expr)
                                                  days-till-start-of-first-full-week)
        total-full-weeks                   (->honeysql driver [:ceil (compiled (h2x// total-full-week-days 7.0))])]
    (->integer driver (h2x/+ 1 total-full-weeks))))

ISO8501 consider the first week of the year is the week that contains the 1st Thursday and week starts on Monday. - If 1st Jan is Friday, then 1st Jan is the last week of previous year. - If 1st Jan is Wednesday, then 1st Jan is in the 1st week.

(defmethod date
  [:sql :week-of-year-iso]
  [_driver _ honeysql-expr]
  (h2x/week honeysql-expr))

US consider the first week begins on 1st Jan, and 2nd week starts on the 1st Sunday

(defmethod date [:sql :week-of-year-us]
  [driver _ honeysql-expr]
  (week-of-year driver honeysql-expr :us))

First week begins on 1st Jan, the 2nd week will begins on the 1st [[metabase.public-settings/start-of-week]]

(defmethod date [:sql :week-of-year-instance]
  [driver _ honeysql-expr]
  (week-of-year driver honeysql-expr :instance))
(defmethod date
  [:sql :day-of-week-iso]
  [driver _ honeysql-expr]
  (binding [driver.common/*start-of-week* :monday]
    (date driver :day-of-week honeysql-expr)))

Return a HoneySQL form that performs represents addition of some temporal interval to the original hsql-form. unit is one of the units listed in [[metabase.util.date-2/add-units]].

(add-interval-honeysql-form :my-driver hsql-form 1 :day) -> [:date_add hsql-form 1 (h2x/literal 'day')]

amount is usually an integer, but can be floating-point for units like seconds.

(defmulti add-interval-honeysql-form
  {:added "0.34.2" :arglists '([driver hsql-form amount unit])}
  driver/dispatch-on-initialized-driver
  :hierarchy #'driver/hierarchy)

Truncate to the day the week starts on.

truncate-fn is a function with the signature

(truncate-fn expr) => truncated-expr

(mu/defn adjust-start-of-week
  [driver      :- :keyword
   truncate-fn :- [:=> [:cat :any] :any]
   expr]
  (let [offset (driver.common/start-of-week-offset driver)]
    (if (not= offset 0)
      (add-interval-honeysql-form driver
                                  (truncate-fn (add-interval-honeysql-form driver expr offset :day))
                                  (- offset) :day)
      (truncate-fn expr))))

Adjust day of week to respect the [[metabase.public-settings/start-of-week]] Setting.

The value a :day-of-week extract should return depends on the value of start-of-week, by default Sunday.

  • 1 = first day of the week (e.g. Sunday)
  • 7 = last day of the week (e.g. Saturday)

This assumes day-of-week as returned by the driver is already between 1 and 7 (adjust it if it's not). It adjusts as needed to match start-of-week by the [[driver.common/start-of-week-offset]], which comes from [[driver/db-start-of-week]].

(mu/defn adjust-day-of-week
  ([driver day-of-week-honeysql-expr]
   (adjust-day-of-week driver day-of-week-honeysql-expr (driver.common/start-of-week-offset driver)))
  ([driver day-of-week-honeysql-expr offset]
   (adjust-day-of-week driver day-of-week-honeysql-expr offset h2x/mod))
  ([driver
    day-of-week-honeysql-expr
    offset :- :int
    mod-fn :- [:=> [:cat any? any?] any?]]
   (cond
     (inline? offset) (recur driver day-of-week-honeysql-expr (second offset) mod-fn)
     (zero? offset)   day-of-week-honeysql-expr
     (neg? offset)    (recur driver day-of-week-honeysql-expr (+ offset 7) mod-fn)
     :else            (-> [:coalesce
                           [:nullif
                            (mod-fn (h2x/+ day-of-week-honeysql-expr offset) (inline-num 7))
                            [:inline 0]]
                           [:inline 7]]
                          (h2x/with-database-type-info (or (h2x/database-type day-of-week-honeysql-expr)
                                                           "integer"))))))

Return the dialect that should be used by Honey SQL 2 when building a SQL statement. Defaults to :ansi, but other valid options are :mysql, :sqlserver, :oracle, and :h2 (added in [[metabase.util.honey-sql-2]]; like :ansi, but uppercases the result). Check [[honey.sql/dialects]] for all available dialects, or register a custom one with [[honey.sql/register-dialect!]].

(honey.sql/format ... :quoting (quote-style driver), :allow-dashed-names? true)

(The name of this method reflects Honey SQL 1 terminology, where "dialect" was called "quote style". To avoid needless churn, I haven't changed it yet. -- Cam)

(defmulti quote-style
  {:added "0.32.0" :arglists '([driver])}
  driver/dispatch-on-initialized-driver
  :hierarchy #'driver/hierarchy)
(defmethod quote-style :sql [_] :ansi)

Return a HoneySQL form appropriate for converting a Unix timestamp integer field or value to an proper SQL Timestamp. seconds-or-milliseconds refers to the resolution of the int in question and with be either :seconds or :milliseconds.

There is a default implementation for :milliseconds the recursively calls with :seconds and (expr / 1000).

(defmulti unix-timestamp->honeysql
  {:arglists '([driver seconds-or-milliseconds honeysql-expr]), :added "0.35.0"}
  (fn [driver seconds-or-milliseconds _] [(driver/dispatch-on-initialized-driver driver) seconds-or-milliseconds])
  :hierarchy #'driver/hierarchy)

Cast a string representing

(defmulti cast-temporal-string
  {:arglists '([driver coercion-strategy honeysql-expr]), :added "0.38.0"}
  (fn [driver coercion-strategy _] [(driver/dispatch-on-initialized-driver driver) coercion-strategy])
  :hierarchy #'driver/hierarchy)
(defmethod cast-temporal-string :default
  [driver coercion-strategy _expr]
  (throw (ex-info (tru "Driver {0} does not support {1}" driver coercion-strategy)
                  {:type qp.error-type/unsupported-feature
                   :coercion-strategy coercion-strategy})))
(defmethod unix-timestamp->honeysql [:sql :milliseconds]
  [driver _ expr]
  (unix-timestamp->honeysql driver :seconds (h2x// expr 1000)))
(defmethod unix-timestamp->honeysql [:sql :microseconds]
  [driver _ expr]
  (unix-timestamp->honeysql driver :seconds (h2x// expr 1000000)))
(defmethod unix-timestamp->honeysql [:sql :nanoseconds]
  [driver _ expr]
  (unix-timestamp->honeysql driver :seconds (h2x// expr 1000000000)))

Cast a byte field

(defmulti cast-temporal-byte
  {:arglists '([driver coercion-strategy expr]), :added "0.38.0"}
  (fn [driver coercion-strategy _] [(driver/dispatch-on-initialized-driver driver) coercion-strategy])
  :hierarchy #'driver/hierarchy)
(defmethod cast-temporal-byte :default
  [driver coercion-strategy _expr]
  (throw (ex-info (tru "Driver {0} does not support {1}" driver coercion-strategy)
                  {:type qp.error-type/unsupported-feature})))

Implementations of this methods define how the SQL Query Processor handles various top-level MBQL clauses. Each method is called when a matching clause is present in query, and should return an appropriately modified version of honeysql-form. Most drivers can use the default implementations for all of these methods, but some may need to override one or more (e.g. SQL Server needs to override this method for the :limit clause, since T-SQL uses TOP instead of LIMIT).

(defmulti apply-top-level-clause
  {:added "0.32.0", :arglists '([driver top-level-clause honeysql-form inner-query]), :style/indent [:form]}
  (fn [driver top-level-clause _honeysql-form _inner-query]
    [(driver/dispatch-on-initialized-driver driver) top-level-clause])
  :hierarchy #'driver/hierarchy)
(defmethod apply-top-level-clause :default
  [_ _ honeysql-form _]
  honeysql-form)

Reaches into a JSON field (that is, a field with a defined :nfc-path).

Lots of SQL DB's have denormalized JSON fields and they all have some sort of special syntax for dealing with indexing into it. Implement the special syntax in this multimethod.

(defmulti json-query
  {:changelog-test/ignore true, :arglists '([driver identifier json-field]), :added "0.43.1"}
  driver/dispatch-on-initialized-driver
  :hierarchy #'driver/hierarchy)

+----------------------------------------------------------------------------------------------------------------+ | inline-value impls | +----------------------------------------------------------------------------------------------------------------+

we can go ahead and add implementations for the classes that implement [[honey.sql.protocols/InlineValue]], except for Object, since we want it to fall back to :default and log a warning

(doseq [[klass {method :sqlize}] (:impls honey.sql.protocols/InlineValue)
        :when (not= klass Object)]
  (.addMethod inline-value [:sql klass] (fn [_driver x]
                                          (method x))))
(defmethod inline-value :default
  [driver object]
  ;; default implementation of [[honey.sql.protocols/sqlize]] is just [[clojure.core/str]], that is almost certainly not
  ;; what we want to do, so log a warning
  (log/warnf "No implementation of %s for [%s %s], falling back to default implementation of %s"
             `inline-value
             driver
             (some-> object class .getCanonicalName)
             `honey.sql.protocols/sqlize)
  (honey.sql.protocols/sqlize object))
(defmethod inline-value [:sql Number]
  [_driver n]
  (str n))
(defmethod inline-value [:sql LocalTime]
  [_driver t]
  (format "time '%s'" (u.date/format "HH:mm:ss.SSS" t)))
(defmethod inline-value [:sql OffsetTime]
  [_driver t]
  (format "time with time zone '%s'" (u.date/format "HH:mm:ss.SSS xxx" t)))
(defmethod inline-value [:sql LocalDate]
  [_driver t]
  (format "date '%s'" (u.date/format t)))
(defmethod inline-value [:sql LocalDateTime]
  [_driver t]
  (format "timestamp '%s'" (u.date/format "yyyy-MM-dd HH:mm:ss.SSS" t)))
(defmethod inline-value [:sql OffsetDateTime]
  [_driver t]
  (format "timestamp with time zone '%s'" (u.date/format "yyyy-MM-dd HH:mm:ss.SSS xxx" t)))
(defmethod inline-value [:sql ZonedDateTime]
  [driver t]
  (inline-value driver (t/offset-date-time t)))

+----------------------------------------------------------------------------------------------------------------+ | Low-Level ->honeysql impls | +----------------------------------------------------------------------------------------------------------------+

[[->honeysql]] shouldn't be getting called on something that is already Honey SQL. Prior to 46/Honey SQL 2, this would not usually cause problems because we could easily distinguish between MBQL clauses and Honey SQL record types; with Honey SQL 2, clauses are basically indistinguishable from MBQL, and some things exist in both, like :/ and :ceil; it's more important that we be careful about avoiding double-compilation to prevent bugs or redundant expressions.

The exception to this rule is [[h2x/identifier]] -- for historical reasons, drivers were encouraged to do this in the past and some rely on this behavior (see ;;; [[metabase.driver.bigquery-cloud-sdk.query-processor]] and [[metabase.driver.snowflake]] for example). Maybe we come up with some better way to handle this -- e.g. maybe [[h2x/identifier]] should be replaced with a sql.qp multimethod so driver-specific behavior can happen as we generate Honey SQL, not afterwards.

If you see this warning, it usually means you are passing a Honey SQL form to a method that expects an MBQL form, usually [[->honeysql]]; this probably means you're recursively calling [[->honeysql]] when you should not be.

You can use [[compiled]] to prevent this error, to work around situations where you need to compile something to Honey SQL and then pass it to a method that expects MBQL. This should be considered an icky HACK and you should only do this if you cannot actually fix your code.

(defn- throw-double-compilation-error
  [driver x]
  ;; not i18n'ed because this is meant to be developer-facing.
  (throw
   (ex-info (format "%s called on something already compiled to Honey SQL, or something unknown. See %s for more info."
                    `->honeysql
                    `throw-double-compilation-error)
            {:driver driver
             :expr   x
             :type   qp.error-type/driver})))
(defmethod ->honeysql :default
  [driver x]
  (when (and (vector? x)
             (keyword? (first x)))
    (throw-double-compilation-error driver x))
  ;; user-facing only so it doesn't need to be i18n'ed
  (throw (ex-info (format "Don't know how to compile %s to Honey SQL: implement %s for %s"
                          (pr-str x)
                          `->honeysql
                          (pr-str [driver (mbql.u/dispatch-by-clause-name-or-class x)]))
                  {:driver driver
                   :expr   x
                   :type   qp.error-type/driver})))
(defmethod ->honeysql [:sql nil]
  [_driver _this]
  nil)
(defmethod ->honeysql [:sql Object]
  [_driver this]
  this)
(defmethod ->honeysql [:sql Number]
  [_driver n]
  (inline-num n))
(defmethod ->honeysql [:sql :value]
  [driver [_ value {base-type :base_type effective-type :effective_type}]]
  (when (some? value)
    (condp #(isa? %2 %1) (or effective-type base-type)
      ;; When we are dealing with a uuid type we should try to convert to a real UUID
      ;; If that fails,, we will add a fallback cast to "text"
      :type/UUID (when (not= "" value) ; support is-empty/non-empty checks
                   (try
                     (UUID/fromString value)
                     (catch IllegalArgumentException _
                       (h2x/with-type-info value {:database-type "varchar"}))))
      (->honeysql driver value))))
(defmethod ->honeysql [:sql :expression]
  [driver [_ expression-name {::add/keys [source-table source-alias]} :as _clause]]
  (let [expression-definition (mbql.u/expression-with-name *inner-query* expression-name)]
    (->honeysql driver (if (= source-table ::add/source)
                         (apply h2x/identifier :field source-query-alias source-alias)
                         expression-definition))))
(defmethod ->honeysql [:sql :now]
  [driver _clause]
  (current-datetime-honeysql-form driver))

Translates coercion types like :Coercion/UNIXSeconds->DateTime to the corresponding unit of time to use in [[unix-timestamp->honeysql]]. Throws an AssertionError if the argument does not descend from :UNIXTime->Temporal and an exception if the type does not have an associated unit.

(defn semantic-type->unix-timestamp-unit
  [coercion-type]
  (when-not (isa? coercion-type :Coercion/UNIXTime->Temporal)
    (throw (ex-info "Semantic type must be a UNIXTimestamp"
                    {:type          qp.error-type/invalid-query
                     :coercion-type coercion-type})))
  (or (get {:Coercion/UNIXNanoSeconds->DateTime  :nanoseconds
            :Coercion/UNIXMicroSeconds->DateTime :microseconds
            :Coercion/UNIXMilliSeconds->DateTime :milliseconds
            :Coercion/UNIXSeconds->DateTime      :seconds}
           coercion-type)
      (throw (Exception. (tru "No magnitude known for {0}" coercion-type)))))

Wrap a field-identifier in appropriate HoneySQL expressions if it refers to a UNIX timestamp Field.

(defn cast-field-if-needed
  [driver {:keys [base-type coercion-strategy], :as field} honeysql-form]
  (if (some #(str/includes? (name %) "_") (keys field))
    (do
      (sql.qp.deprecated/log-deprecation-warning
       driver
       "metabase.driver.sql.query-processor/cast-field-id-needed with a legacy (snake_cased) :model/Field"
       "0.48.0")
      (recur driver (update-keys field u/->kebab-case-en) honeysql-form))
    (u/prog1 (match [base-type coercion-strategy]
               [(:isa? :type/Number) (:isa? :Coercion/UNIXTime->Temporal)]
               (unix-timestamp->honeysql driver
                                         (semantic-type->unix-timestamp-unit coercion-strategy)
                                         honeysql-form)
               [:type/Text (:isa? :Coercion/String->Temporal)]
               (cast-temporal-string driver coercion-strategy honeysql-form)
               [(:isa? :type/*) (:isa? :Coercion/Bytes->Temporal)]
               (cast-temporal-byte driver coercion-strategy honeysql-form)
               :else honeysql-form)
      (when-not (= <> honeysql-form)
        (log/tracef "Applied casting\n=>\n%s" (u/pprint-to-str <>))))))

it's a little weird that we're calling [[->honeysql]] on an identifier, which is a Honey SQL form and not an MBQL form. See [[throw-double-compilation-error]] for more info.

(defmethod ->honeysql [:sql ::h2x/identifier]
  [_driver identifier]
  identifier)

Apply temporal bucketing for the :temporal-unit in the options of a :field clause; return a new HoneySQL form that buckets honeysql-form appropriately.

(defn apply-temporal-bucketing
  [driver {:keys [temporal-unit]} honeysql-form]
  (date driver temporal-unit honeysql-form))

Apply :binning options from a :field clause; return a new HoneySQL form that bins honeysql-form appropriately.

(defn apply-binning
  [{{:keys [bin-width min-value _max-value]} :binning} honeysql-form]
  ;;
  ;; Equation is | (value - min) |
  ;;             | ------------- | * bin-width + min-value
  ;;             |_  bin-width  _|
  ;;
  (cond-> honeysql-form
    (not (zero? min-value)) (h2x/- min-value)
    true                    (h2x// bin-width)
    true                    h2x/floor
    true                    (h2x/* bin-width)
    (not (zero? min-value)) (h2x/+ min-value)))
(mu/defn- field-source-table-aliases :- [:maybe [:sequential ::lib.schema.common/non-blank-string]]
  "Get sequence of alias that should be used to qualify a `:field` clause when compiling (e.g. left-hand side of an
  `AS`).
    (field-source-table-aliases [:field 1 nil]) ; -> [\"public\" \"venues\"]"
  [[_ id-or-name {::add/keys [source-table]}]]
  (let [source-table (or source-table
                         (when (integer? id-or-name)
                           (:table-id (lib.metadata/field (qp.store/metadata-provider) id-or-name))))]
    (cond
      (= source-table ::add/source) [source-query-alias]
      (= source-table ::add/none)   nil
      (integer? source-table)       (let [{schema :schema, table-name :name} (lib.metadata/table
                                                                              (qp.store/metadata-provider)
                                                                              source-table)]
                                      (not-empty (filterv some? [schema table-name])))
      source-table                  [source-table])))

Get alias that should be use to refer to a :field clause when compiling (e.g. left-hand side of an AS).

(field-source-alias [:field 1 nil]) ; -> "price"

(defn- field-source-alias
  [[_field id-or-name {::add/keys [source-alias]}]]
  (or source-alias
      (when (string? id-or-name)
        id-or-name)
      (when (integer? id-or-name)
        (:name (lib.metadata/field (qp.store/metadata-provider) id-or-name)))))
(defn- field-nfc-path
  [[_field id-or-name {::add/keys [nfc-path]}]]
  (or nfc-path
      (when (integer? id-or-name)
        (:nfc-path (lib.metadata/field (qp.store/metadata-provider) id-or-name)))))
(defmethod ->honeysql [:sql ::nfc-path]
  [_driver [_ _nfc-path]]
  nil)
(defmethod ->honeysql [:sql :field]
  [driver [_ id-or-name {:keys [database-type] :as options}
           :as field-clause]]
  (try
    (let [source-table-aliases (field-source-table-aliases field-clause)
          source-nfc-path      (field-nfc-path field-clause)
          source-alias         (field-source-alias field-clause)
          field                (when (integer? id-or-name)
                                 (lib.metadata/field (qp.store/metadata-provider) id-or-name))
          allow-casting?       (and field
                                    (not (:qp/ignore-coercion options)))
          database-type        (or database-type
                                   (:database-type field))
          ;; preserve metadata attached to the original field clause, for example BigQuery temporal type information.
          identifier           (-> (apply h2x/identifier :field
                                          (concat source-table-aliases (->honeysql driver [::nfc-path source-nfc-path]) [source-alias]))
                                   (with-meta (meta field-clause)))
          identifier           (->honeysql driver identifier)
          maybe-add-db-type    (fn [expr]
                                 (if (h2x/type-info->db-type (h2x/type-info expr))
                                   expr
                                   (h2x/with-database-type-info expr database-type)))]
      (u/prog1
        (cond->> identifier
          allow-casting?           (cast-field-if-needed driver field)
          ;; only add type info if it wasn't added by [[cast-field-if-needed]]
          database-type            maybe-add-db-type
          (:temporal-unit options) (apply-temporal-bucketing driver options)
          (:binning options)       (apply-binning options))
        (log/trace (binding [*print-meta* true]
                     (format "Compiled field clause\n%s\n=>\n%s"
                             (u/pprint-to-str field-clause) (u/pprint-to-str <>))))))
    (catch Throwable e
      (throw (ex-info (tru "Error compiling :field clause: {0}" (ex-message e))
                      {:clause field-clause}
                      e)))))
(defmethod ->honeysql [:sql :count]
  [driver [_ field]]
  (if field
    [:count (->honeysql driver field)]
    :%count.*))
(defmethod ->honeysql [:sql :avg]    [driver [_ field]] [:avg        (->honeysql driver field)])
(defmethod ->honeysql [:sql :median] [driver [_ field]] [:median     (->honeysql driver field)])
(defmethod ->honeysql [:sql :stddev] [driver [_ field]] [:stddev_pop (->honeysql driver field)])
(defmethod ->honeysql [:sql :var]    [driver [_ field]] [:var_pop    (->honeysql driver field)])
(defmethod ->honeysql [:sql :sum]    [driver [_ field]] [:sum        (->honeysql driver field)])
(defmethod ->honeysql [:sql :min]    [driver [_ field]] [:min        (->honeysql driver field)])
(defmethod ->honeysql [:sql :max]    [driver [_ field]] [:max        (->honeysql driver field)])
(defmethod ->honeysql [:sql :percentile]
  [driver [_ field p]]
  (let [field (->honeysql driver field)
        p     (->honeysql driver p)]
    [::h2x/percentile-cont field p]))
(defmethod ->honeysql [:sql :distinct]
  [driver [_ field]]
  (let [field (->honeysql driver field)]
    [::h2x/distinct-count field]))
(defmethod ->honeysql [:sql :floor] [driver [_ mbql-expr]] [:floor (->honeysql driver mbql-expr)])
(defmethod ->honeysql [:sql :ceil]  [driver [_ mbql-expr]] [:ceil  (->honeysql driver mbql-expr)])
(defmethod ->honeysql [:sql :round] [driver [_ mbql-expr]] [:round (->honeysql driver mbql-expr)])
(defmethod ->honeysql [:sql :abs]   [driver [_ mbql-expr]] [:abs (->honeysql driver mbql-expr)])
(defmethod ->honeysql [:sql :log]   [driver [_ mbql-expr]] [:log (inline-num 10) (->honeysql driver mbql-expr)])
(defmethod ->honeysql [:sql :exp]   [driver [_ mbql-expr]] [:exp (->honeysql driver mbql-expr)])
(defmethod ->honeysql [:sql :sqrt]  [driver [_ mbql-expr]] [:sqrt (->honeysql driver mbql-expr)])
(defmethod ->honeysql [:sql :power]
  [driver [_power mbql-expr power]]
  [:power
   (->honeysql driver mbql-expr)
   (->honeysql driver power)])
(defn- aggregation?
  [expr]
  (and (vector? expr)
       (> (count expr) 1)
       (= (first expr) :aggregation)
       (int? (second expr))))
(defn- unwrap-aggregation-option
  [agg]
  (cond-> agg
    (and (vector? agg) (= (first agg) :aggregation-options)) second))

Returns a vector containing the aggregations specified by order-bys compiled to honeysql expressions for driver suitable for ordering in the over clause of a window function.

(defn- over-order-bys
  [driver aggregations order-bys]
  (let [aggregations (vec aggregations)]
    (into []
          (keep (fn [[direction expr]]
                  (if (aggregation? expr)
                    (let [[_aggregation index] expr
                          agg (unwrap-aggregation-option (aggregations index))]
                      (when-not (#{:cum-count :cum-sum :offset} (first agg))
                        [(->honeysql driver agg) direction]))
                    [(->honeysql driver expr) direction])))
          order-bys)))

Order by the first breakout, then partition by all the other ones. See #42003 and https://metaboat.slack.com/archives/C05MPF0TM3L/p1714084449574689 for more info.

(defn- window-aggregation-over-expr-for-query-with-breakouts
  [driver inner-query]
  (let [breakouts (:breakout inner-query)
        group-bys (:group-by (apply-top-level-clause driver :breakout {} inner-query))
        finest-temp-breakout (qp.util.transformations.nest-breakouts/finest-temporal-breakout-index breakouts 2)
        partition-exprs (when (> (count breakouts) 1)
                          (if finest-temp-breakout
                            (m/remove-nth finest-temp-breakout group-bys)
                            (butlast group-bys)))
        order-bys (over-order-bys driver (:aggregation inner-query) (:order-by inner-query))]
    (merge
     (when (seq partition-exprs)
       {:partition-by (mapv (fn [expr]
                              [expr])
                            partition-exprs)})
     {:order-by order-bys})))
(defn- window-aggregation-over-expr-for-query-without-breakouts [driver inner-query]
  (when-let [order-bys (not-empty (:order-by (apply-top-level-clause driver :order-by {} inner-query)))]
    {:order-by (vec order-bys)}))

Generate an OVER (...) window function expression for stuff like :offset (lag and lead).

(defn- window-aggregation-over-rows
  ([driver expr]
   (window-aggregation-over-rows driver expr nil))
  ([driver expr additional-hsql]
   (let [f (cond
             (seq (:breakout *inner-query*))
             window-aggregation-over-expr-for-query-with-breakouts
             (seq (:order-by *inner-query*))
             window-aggregation-over-expr-for-query-without-breakouts
             :else
             (throw (ex-info (tru "Window function requires either breakouts or order by in the query")
                             {:type  qp.error-type/invalid-query
                              :query *inner-query*})))
         m (f driver *inner-query*)]
     (-> [:over [expr (merge m additional-hsql)]]
         (h2x/with-database-type-info (h2x/database-type expr))))))
(defn- format-rows-unbounded-preceding [_clause _args]
  ["ROWS UNBOUNDED PRECEDING"])
(sql/register-clause!
 ::rows-unbounded-preceding
 #'format-rows-unbounded-preceding
 nil)

Generate an OVER (...) expression for stuff like cumulative sum or cumulative count.

For a single breakout the generated SQL will look something like:

OVER ( ORDER BY created_at ROWS UNBOUNDED PRECEDING )

Note that [[nest-breakouts-in-queries-with-window-fn-aggregations]] ensures we will always see a plain column identifier here.

With more than one breakout, we PARTITION BY all breakouts except the last, then ORDER BY the last breakout. See

2862 for more information as to why we do this. Example:

OVER ( PARTITION BY city_name ORDER BY created_at ROWS UNBOUNDED PRECEDING )

(defn- cumulative-aggregation-over-rows
  [driver expr]
  (window-aggregation-over-rows driver expr {::rows-unbounded-preceding []}))

cum-count()

should compile to SQL like

sum(count()) OVER (ORDER BY ...)

where the ORDER BY matches what's in the query (i.e., the breakouts), or

sum(count()) OVER (ORDER BY 1 ROWS UNBOUNDED PRECEDING)

if the database supports ordering by SELECT expression position

(defmethod ->honeysql [:sql :cum-count]
  [driver [_cum-count expr-or-nil]]
  ;; a cumulative count with no breakouts doesn't really mean anything, just compile it as a normal count.
  (if (empty? (:breakout *inner-query*))
    (->honeysql driver [:count expr-or-nil])
    (cumulative-aggregation-over-rows
     driver
     [:sum (if expr-or-nil
             [:count (->honeysql driver expr-or-nil)]
             [:count :*])])))

cum-sum(total)

should compile to SQL like

sum(sum(total)) OVER (ORDER BY ...)

where the ORDER BY matches what's in the query (i.e., the breakouts), or

sum(sum(total)) OVER (ORDER BY 1 ROWS UNBOUNDED PRECEDING)

if the database supports ordering by SELECT expression position

(defmethod ->honeysql [:sql :cum-sum]
  [driver [_cum-sum expr]]
  ;; a cumulative sum with no breakouts doesn't really mean anything, just compile it as a normal sum.
  (if (empty? (:breakout *inner-query*))
    (->honeysql driver [:sum expr])
    (cumulative-aggregation-over-rows
     driver
     [:sum [:sum (->honeysql driver expr)]])))
(defmethod ->honeysql [:sql :offset]
  [driver [_offset _opts expr n]]
  {:pre [(integer? n) ((some-fn pos-int? neg-int?) n)]} ; offset not allowed to be zero
  (window-aggregation-over-rows
   driver
   (let [[f n]     (if (pos? n)
                     [:lead n]
                     [:lag (- n)])
         expr-hsql (->honeysql driver expr)]
     (-> [f expr-hsql [:inline n]]
         (h2x/with-database-type-info (h2x/database-type expr-hsql))))))
(defn- interval? [expr]
  (mbql.u/is-clause? :interval expr))
(defmethod ->honeysql [:sql :+]
  [driver [_ & args]]
  (if (some interval? args)
    (if-let [[field intervals] (u/pick-first (complement interval?) args)]
      (reduce (fn [hsql-form [_ amount unit]]
                (add-interval-honeysql-form driver hsql-form amount unit))
              (->honeysql driver field)
              intervals)
      (throw (ex-info "Summing intervals is not supported" {:args args})))
    (into [:+]
          (map (partial ->honeysql driver))
          args)))
(defmethod ->honeysql [:sql :-]
  [driver [_ & [first-arg & other-args :as args]]]
  (cond (interval? first-arg)
        (throw (ex-info (tru "Interval as first argrument to subtraction is not allowed.")
                        {:type qp.error-type/invalid-query
                         :args args}))
        (and (some interval? other-args)
             (not (every? interval? other-args)))
        (throw (ex-info (tru "All but first argument to subtraction must be an interval.")
                        {:type qp.error-type/invalid-query
                         :args args})))
  (if (interval? (first other-args))
    (reduce (fn [hsql-form [_ amount unit]]
              ;; We are adding negative amount. Inspired by `->honeysql [:sql :datetime-subtract]`.
              (add-interval-honeysql-form driver hsql-form (- amount) unit))
            (->honeysql driver first-arg)
            other-args)
    (into [:-]
          (map (partial ->honeysql driver))
          args)))
(defmethod ->honeysql [:sql :*]
  [driver [_ & args]]
  (into [:*]
        (map (partial ->honeysql driver))
        args))

for division we want to go ahead and convert any integer args to floats, because something like field / 2 will do integer division and give us something like 1.0 where we would rather see something like 1.5

also, we want to gracefully handle situations where the column is ZERO and just swap it out with NULL instead, so we don't get divide by zero errors. SQL DBs always return NULL when dividing by NULL (AFAIK)

Make sure we're not trying to divide by zero.

(defn- safe-denominator
  [denominator]
  (cond
    ;; try not to generate hairy nonsense like `CASE WHERE 7.0 = 0 THEN NULL ELSE 7.0` if we're dealing with number
    ;; literals and can determine this stuff ahead of time.
    (and (number? denominator)
         (zero? denominator))
    nil
    (number? denominator)
    (inline-num denominator)
    (inline? denominator)
    (recur (second denominator))
    :else
    [:nullif denominator [:inline 0]]))
(defmethod ->honeysql [:sql :/]
  [driver [_ & mbql-exprs]]
  (let [[numerator & denominators] (for [mbql-expr mbql-exprs]
                                     (->honeysql driver (if (integer? mbql-expr)
                                                          (double mbql-expr)
                                                          mbql-expr)))]
    (into [:/ (->float driver numerator)]
          (map safe-denominator)
          denominators)))
(defmethod ->honeysql [:sql :sum-where]
  [driver [_ arg pred]]
  [:sum [:case
         (->honeysql driver pred) (->honeysql driver arg)
         :else                    [:inline 0.0]]])
(defmethod ->honeysql [:sql :count-where]
  [driver [_ pred]]
  (->honeysql driver [:sum-where 1 pred]))
(defmethod ->honeysql [:sql :share]
  [driver [_ pred]]
  [:/ (->honeysql driver [:count-where pred]) :%count.*])
(defmethod ->honeysql [:sql :trim]
  [driver [_ arg]]
  [:trim (->honeysql driver arg)])
(defmethod ->honeysql [:sql :ltrim]
  [driver [_ arg]]
  [:ltrim (->honeysql driver arg)])
(defmethod ->honeysql [:sql :rtrim]
  [driver [_ arg]]
  [:rtrim (->honeysql driver arg)])
(defmethod ->honeysql [:sql :upper]
  [driver [_ arg]]
  [:upper (->honeysql driver arg)])
(defmethod ->honeysql [:sql :lower]
  [driver [_ arg]]
  [:lower (->honeysql driver arg)])
(defmethod ->honeysql [:sql :coalesce]
  [driver [_ & args]]
  (into [:coalesce] (map (partial ->honeysql driver)) args))
(defmethod ->honeysql [:sql :replace]
  [driver [_ arg pattern replacement]]
  [:replace (->honeysql driver arg) (->honeysql driver pattern) (->honeysql driver replacement)])
(defmethod ->honeysql [:sql :concat]
  [driver [_ & args]]
  (into [:concat] (map (partial ->honeysql driver)) args))
(defmethod ->honeysql [:sql :substring]
  [driver [_ arg start length]]
  (if length
    [:substring (->honeysql driver arg) (->honeysql driver start) (->honeysql driver length)]
    [:substring (->honeysql driver arg) (->honeysql driver start)]))
(defmethod ->honeysql [:sql :length]
  [driver [_ arg]]
  [:length (->honeysql driver arg)])
(defmethod ->honeysql [:sql :case]
  [driver [_ cases options]]
  (into [:case]
        (comp cat
              (map (partial ->honeysql driver)))
        (concat cases
                (when (some? (:default options))
                  [[:else (:default options)]]))))

actual handling of the name is done in the top-level clause handler for aggregations

(defmethod ->honeysql [:sql :aggregation-options]
  [driver [_ ag]]
  (->honeysql driver ag))

aggregation REFERENCE e.g. the ["aggregation" 0] fields we allow in order-by

(defmethod ->honeysql [:sql :aggregation]
  [driver [_ index]]
  (lib.util.match/match-one (nth (:aggregation *inner-query*) index)
    [:aggregation-options ag (options :guard :name)]
    (->honeysql driver (h2x/identifier :field-alias (:name options)))

    [:aggregation-options ag _]
    #_:clj-kondo/ignore
    (recur ag)

    ;; For some arcane reason we name the results of a distinct aggregation "count", everything else is named the
    ;; same as the aggregation
    :distinct
    (->honeysql driver (h2x/identifier :field-alias :count))

    #{:+ :- :* :/}
    (->honeysql driver &match)

    [:offset (options :guard :name) _expr _n]
    (->honeysql driver (h2x/identifier :field-alias (:name options)))

    ;; for everything else just use the name of the aggregation as an identifer, e.g. `:sum`
    ;;
    ;; TODO -- I don't think we will ever actually get to this anymore because everything should have been given a name
    ;; by [[metabase.query-processor.middleware.pre-alias-aggregations]]
    [ag-type & _]
    (->honeysql driver (h2x/identifier :field-alias ag-type))))
(mu/defmethod ->honeysql [:sql :absolute-datetime] :- some?
  [driver [_ timestamp unit]]
  (date driver unit (->honeysql driver timestamp)))
(mu/defmethod ->honeysql [:sql :time] :- some?
  [driver [_ value unit]]
  (date driver unit (->honeysql driver value)))
(mu/defmethod ->honeysql [:sql :relative-datetime] :- some?
  [driver [_ amount unit]]
  (date driver unit (if (zero? amount)
                      (current-datetime-honeysql-form driver)
                      (add-interval-honeysql-form driver (current-datetime-honeysql-form driver) amount unit))))
(defmethod ->honeysql [:sql :temporal-extract]
  [driver [_ mbql-expr unit]]
  (date driver unit (->honeysql driver mbql-expr)))
(defmethod ->honeysql [:sql :datetime-add]
  [driver [_ arg amount unit]]
  (add-interval-honeysql-form driver (->honeysql driver arg) amount unit))
(defmethod ->honeysql [:sql :datetime-subtract]
  [driver [_ arg amount unit]]
  (add-interval-honeysql-form driver (->honeysql driver arg) (- amount) unit))

This util function is used by SQL implementations of ->honeysql for the :datetime-diff clause. It raises an exception if the database-type of the arguments x and y do not match the given predicate. Note this doesn't raise an error if the database-type is nil, which can be the case for some drivers.

(defn datetime-diff-check-args
  [x y pred]
  (doseq [arg [x y]
          :let [db-type (h2x/database-type arg)]
          :when (and db-type (not (pred db-type)))]
    (throw (ex-info (tru "datetimeDiff only allows datetime, timestamp, or date types. Found {0}"
                         (pr-str db-type))
                    {:found db-type
                     :type  qp.error-type/invalid-query}))))
(defmethod ->honeysql [:sql :datetime-diff]
  [driver [_ x y unit]]
  (let [x (->honeysql driver x)
        y (->honeysql driver y)]
    (datetime-diff-check-args x y (partial re-find #"(?i)^(timestamp|date)"))
    (datetime-diff driver unit x y)))

+----------------------------------------------------------------------------------------------------------------+ | Field Aliases (AS Forms) | +----------------------------------------------------------------------------------------------------------------+

TODO -- this name is a bit of a misnomer since it also handles :aggregation and :expression clauses.

(mu/defn field-clause->alias :- some?
  "Generate HoneySQL for an approriate alias (e.g., for use with SQL `AS`) for a `:field`, `:expression`, or
  `:aggregation` clause of any type, or `nil` if the Field should not be aliased. By default uses the
  `::add/desired-alias` key in the clause options.
  Optional third parameter `unique-name-fn` is no longer used as of 0.42.0."
  ([driver                                                :- :keyword
    [clause-type id-or-name {::add/keys [desired-alias]}] :- vector?]
   (let [desired-alias (or desired-alias
                           ;; fallback behavior for anyone using SQL QP functions directly without including the stuff
                           ;; from [[metabase.query-processor.util.add-alias-info]]. We should probably disallow this
                           ;; going forward because it is liable to break
                           (when (string? id-or-name)
                             id-or-name)
                           (when (and (= clause-type :field)
                                      (integer? id-or-name))
                             (:name (lib.metadata/field (qp.store/metadata-provider) id-or-name))))]
     (->honeysql driver (h2x/identifier :field-alias desired-alias))))
  ([driver field-clause _unique-name-fn]
   (sql.qp.deprecated/log-deprecation-warning
    driver
    "metabase.driver.sql.query-processor/field-clause->alias with 3 args"
    "0.48.0")
   (field-clause->alias driver field-clause)))

Generate HoneySQL for an AS form (e.g. <form> AS <field>) using the name information of a clause. The HoneySQL representation of on AS clause is a tuple like [<form> <alias>].

In some cases where the alias would be redundant, such as plain field literals, this returns the form as-is for Honey SQL 1. It's wrapped in a vector for Honey SQL 2 to eliminate ambiguity if the clause compiles to a Honey SQL vector. This is not allowed in Honey SQL 1 -- [expr alias] always has to have an alias.

Honey SQL 2 seems to actually need an additional vector around the alias form, otherwise it doesn't work correctly. See https://clojurians.slack.com/archives/C1Q164V29/p1675301408026759

;; Honey SQL 1 (as [:field "x" {:base-type :type/Text}]) ;; -> (Identifier ...) ;; -> SELECT "x"

;; Honey SQL 2 (as [:field "x" {:base-type :type/Text}]) ;; -> [[::h2x/identifier ...]] ;; -> SELECT "x"

;; Honey SQL 1 (as [:field "x" {:base-type :type/Text, :temporal-unit :month}]) ;; -> [(Identifier ...) (Identifier ...)] ;; -> SELECT date_extract("x", 'month') AS "x"

;; Honey SQL 2 (as [:field "x" {:base-type :type/Text, :temporal-unit :month}]) ;; -> [[::h2x/identifier ...] [[::h2x/identifier ...]]] ;; -> SELECT date_extract("x", 'month') AS "x"

(defn as
  [driver clause & _unique-name-fn]
  (let [honeysql-form (->honeysql driver clause)
        field-alias   (field-clause->alias driver clause)]
    (if field-alias
      [honeysql-form [field-alias]]
      [honeysql-form])))

Certain SQL drivers require that we refer to Fields using the alias we give in the SELECT clause in ORDER BY and GROUP BY rather than repeating definitions. BigQuery does this generally, other DB's require this in JSON columns.

See #17536 and #18742

Rewrite :field clauses to force them to use the column alias regardless of where they appear.

(defn rewrite-fields-to-force-using-column-aliases
  ([form]
   (rewrite-fields-to-force-using-column-aliases form {:is-breakout false}))
  ([form {is-breakout :is-breakout}]
   (lib.util.match/replace form
     [:field id-or-name opts]
     [:field id-or-name (cond-> opts
                          true
                          (assoc ::add/source-alias        (::add/desired-alias opts)
                                 ::add/source-table        ::add/none
                                 ;; this key will tell the SQL QP not to apply casting here either.
                                 :qp/ignore-coercion       true
                                 ;; used to indicate that this is a forced alias
                                 ::forced-alias            true)
                          ;; don't want to do temporal bucketing or binning inside the order by only.
                          ;; That happens inside the `SELECT`
                          ;; (#22831) however, we do want it in breakout
                          (not is-breakout)
                          (dissoc :temporal-unit :binning))])))

+----------------------------------------------------------------------------------------------------------------+ | Clause Handlers | +----------------------------------------------------------------------------------------------------------------+

-------------------------------------------------- aggregation ---------------------------------------------------

(defmethod apply-top-level-clause [:sql :aggregation]
  [driver _top-level-clause honeysql-form {aggregations :aggregation, :as inner-query}]
  (let [honeysql-ags (vec (for [ag   aggregations
                                :let [ag-expr  (->honeysql driver ag)
                                      ag-name  (annotate/aggregation-name inner-query ag)
                                      ag-alias (->honeysql driver (h2x/identifier
                                                                   :field-alias
                                                                   (driver/escape-alias driver ag-name)))]]
                            [ag-expr [ag-alias]]))]
    (reduce (if (:select-top honeysql-form)
              sql.helpers/select-top
              sql.helpers/select)
            honeysql-form
            honeysql-ags)))

----------------------------------------------- breakout & fields ------------------------------------------------

(defmethod apply-top-level-clause [:sql :breakout]
  [driver _ honeysql-form {breakout-fields :breakout, fields-fields :fields :as _query}]
  (let [select (if (:select-top honeysql-form)
                 sql.helpers/select-top
                 sql.helpers/select)]
    (as-> honeysql-form new-hsql
      (apply select new-hsql (->> breakout-fields
                                  (remove (set fields-fields))
                                  (mapv (fn [field-clause]
                                          (as driver field-clause)))))
      (apply sql.helpers/group-by new-hsql (mapv (partial ->honeysql driver) breakout-fields)))))
(defmethod apply-top-level-clause [:sql :fields]
  [driver _ honeysql-form {fields :fields}]
  (apply (if (:select-top honeysql-form)
           sql.helpers/select-top
           sql.helpers/select)
         honeysql-form
         (for [field-clause fields]
           (as driver field-clause))))

----------------------------------------------------- filter -----------------------------------------------------

Generate honeysql like clause used in :starts-with, :contains or `:ends-with. If matching case insensitively, pattern is lowercased earlier in [[generate-pattern]].

(defn- like-clause
  [field pattern {:keys [case-sensitive] :or {case-sensitive true} :as _options}]
  ;; TODO - don't we need to escape underscores and percent signs in the pattern, since they have special meanings in
  ;; LIKE clauses? That's what we're doing with Druid... (Cam)
  ;;
  ;; TODO - Postgres supports `ILIKE`. Does that make a big enough difference performance-wise that we should do a
  ;; custom implementation? (Cam)
  [:like
   (if case-sensitive
     field
     [:lower field])
   pattern])
(def ^:private StringValueOrFieldOrExpression
  [:or
   [:and mbql.s/value
    [:fn {:error/message "string value"} #(string? (second %))]]
   ::mbql.s/FieldOrExpressionDef])

Generate pattern to match against in like clause. Lowercasing for case insensitive matching also happens here.

(mu/defn- generate-pattern
  [driver
   pre
   [type _ :as arg] :- StringValueOrFieldOrExpression
   post
   {:keys [case-sensitive] :or {case-sensitive true} :as _options}]
  (if (= :value type)
    (->honeysql driver (update arg 1 #(cond-> (str pre % post)
                                        (not case-sensitive) u/lower-case-en)))
    (let [expr (->honeysql driver (into [:concat] (remove nil?) [pre arg post]))]
      (if case-sensitive
        expr
        [:lower expr]))))
(defn- uuid-field?
  [x]
  (and (mbql.u/mbql-clause? x)
       (isa? (or (:effective-type (get x 2))
                 (:base-type (get x 2)))
             :type/UUID)))

For := and :!=. Comparing UUID fields against non-uuid values requires casting.

(mu/defn- maybe-cast-uuid-for-equality
  [driver field arg]
  (if (and (uuid-field? field)
             ;; If the arg is a uuid we are happy especially for joins (#46558)
           (not (uuid-field? arg))
             ;; If we could not convert the arg to a UUID then we have to cast the Field.
             ;; This will not hit indexes, but then we're passing an arg that can only be compared textually.
           (not (uuid? (->honeysql driver arg)))
             ;; Check for inlined values
           (not (= (:database-type (h2x/type-info (->honeysql driver arg))) "uuid")))
    [::cast-to-text field]
    field))

For :contains, :starts-with, and :ends-with. Comparing UUID fields against with these operations requires casting as the right side will have % for LIKE operations.

(mu/defn- maybe-cast-uuid-for-text-compare
  [field]
  (if (uuid-field? field)
    [::cast-to-text field]
    field))
(defmethod ->honeysql [:sql ::cast]
  [driver [_ expr database-type]]
  (h2x/maybe-cast database-type (->honeysql driver expr)))
(defmethod ->honeysql [:sql ::cast-to-text]
  [driver [_ expr]]
  ;; Oracle does not support text type,
  ;; sqlserver limits varchar to 30 in casts,
  ;; athena cannot cast uuid to bounded varchars
  (->honeysql driver [::cast expr "text"]))
(defmethod ->honeysql [:sql :starts-with]
  [driver [_ field arg options]]
  (like-clause (->honeysql driver (maybe-cast-uuid-for-text-compare field))
               (generate-pattern driver nil arg "%" options) options))
(defmethod ->honeysql [:sql :contains]
  [driver [_ field arg options]]
  (like-clause (->honeysql driver (maybe-cast-uuid-for-text-compare field))
               (generate-pattern driver "%" arg "%" options) options))
(defmethod ->honeysql [:sql :ends-with]
  [driver [_ field arg options]]
  (like-clause (->honeysql driver (maybe-cast-uuid-for-text-compare field))
               (generate-pattern driver "%" arg nil options) options))
(defn- parent-honeysql-col-base-type-map
  [field]
  (when (and (vector? field)
             (= 3 (count field))
             (= :field (first field))
             (map? (field 2)))
    (select-keys (field 2) [:base-type])))

To be bound in ->honeysql <driver> <op> where op is on of {:>, :>=, :<, :<=, :=, :between}`. Its value should be {:base-type keyword? :database-type string?}. The value is used in ->honeysql <driver> :relative-datetime, the :snowflake implementation at the time of writing, and later in the [[metabase.query-processor.util.relative-datetime/maybe-cacheable-relative-datetime-honeysql]] to determine (1) format of server-side generated sql temporal string and (2) the database type it should be cast to.

(def ^:dynamic *parent-honeysql-col-type-info*
  nil)
(defmethod ->honeysql [:sql :between]
  [driver [_ field min-val max-val]]
  (let [field-honeysql (->honeysql driver field)]
    (binding [*parent-honeysql-col-type-info* (merge (when-let [database-type (h2x/database-type field-honeysql)]
                                                       {:database-type database-type})
                                                     (parent-honeysql-col-base-type-map field))]
      [:between field-honeysql (->honeysql driver min-val) (->honeysql driver max-val)])))
(doseq [operator [:> :>= :< :<=]]
  (defmethod ->honeysql [:sql operator] ; [:> :>= :< :<=] -- For grep.
    [driver [_ field value]]
    (let [field-honeysql (->honeysql driver field)]
      (binding [*parent-honeysql-col-type-info* (merge (when-let [database-type (h2x/database-type field-honeysql)]
                                                         {:database-type database-type})
                                                       (parent-honeysql-col-base-type-map field))]
        [operator field-honeysql (->honeysql driver value)]))))
(defmethod ->honeysql [:sql :=]
  [driver [_ field value]]
  (assert field)
  (let [field-honeysql (->honeysql driver (maybe-cast-uuid-for-equality driver field value))]
    (binding [*parent-honeysql-col-type-info* (merge (when-let [database-type (h2x/database-type field-honeysql)]
                                                       {:database-type database-type})
                                                     (parent-honeysql-col-base-type-map field))]
      [:= field-honeysql (->honeysql driver value)])))
(defn- correct-null-behaviour
  [driver [op & args :as clause]]
  (if-let [field-arg (lib.util.match/match-one args
                       :field          &match
                       :expression     &match)]
    ;; We must not transform the head again else we'll have an infinite loop
    ;; (and we can't do it at the call-site as then it will be harder to fish out field references)
    [:or
     (into [op] (map (partial ->honeysql driver)) args)
     [:= (->honeysql driver field-arg) nil]]
    clause))
(defmethod ->honeysql [:sql :!=]
  [driver [_ field value]]
  (if (nil? (qp.wrap-value-literals/unwrap-value-literal value))
    [:not= (->honeysql driver (maybe-cast-uuid-for-equality driver field value)) (->honeysql driver value)]
    (correct-null-behaviour driver [:not= (maybe-cast-uuid-for-equality driver field value) value])))
(defmethod ->honeysql [:sql :and]
  [driver [_tag & subclauses]]
  (into [:and]
        (map (partial ->honeysql driver))
        subclauses))
(defmethod ->honeysql [:sql :or]
  [driver [_tag & subclauses]]
  (into [:or]
        (map (partial ->honeysql driver))
        subclauses))
(def ^:private clause-needs-null-behaviour-correction?
  (comp #{:contains :starts-with :ends-with} first))
(defmethod ->honeysql [:sql :not]
  [driver [_tag subclause]]
  (if (clause-needs-null-behaviour-correction? subclause)
    (correct-null-behaviour driver [:not subclause])
    [:not (->honeysql driver subclause)]))
(defmethod apply-top-level-clause [:sql :filter]
  [driver _ honeysql-form {clause :filter}]
  (sql.helpers/where honeysql-form (->honeysql driver clause)))

-------------------------------------------------- join tables ---------------------------------------------------

(declare mbql->honeysql)

Compile a single MBQL join to HoneySQL.

(defmulti join->honeysql
  {:added "0.32.9" :arglists '([driver join])}
  driver/dispatch-on-initialized-driver
  :hierarchy #'driver/hierarchy)

Generate HoneySQL for a table or query to be joined.

(defmulti join-source
  {:added "0.32.9" :arglists '([driver join])}
  driver/dispatch-on-initialized-driver
  :hierarchy #'driver/hierarchy)
(defmethod join-source :sql
  [driver {:keys [source-table source-query]}]
  (cond
    (and source-query (:native source-query))
    (sql-source-query (:native source-query) (:params source-query))

    source-query
    (mbql->honeysql driver {:query source-query})

    :else
    (->honeysql driver (lib.metadata/table (qp.store/metadata-provider) source-table))))

Schema for HoneySQL for a single JOIN. Used to validate that our join-handling code generates correct clauses.

(def ^:private HoneySQLJoin
  [:tuple
   ;;join source and alias
   [:tuple
    ;; join source
    :some
    ;; join alias
    :some]
   ;; join condition
   [:sequential :any]])
(mu/defmethod join->honeysql :sql :- HoneySQLJoin
  [driver {:keys [condition], join-alias :alias, :as join} :- mbql.s/Join]
  [[(join-source driver join)
    (let [table-alias (->honeysql driver (h2x/identifier :table-alias join-alias))]
      [table-alias])]
   (->honeysql driver condition)])

Use Honey SQL 2's :join-by so the joins are in the same order they are specified in MBQL (#15342). See [[metabase.query-processor-test.explicit-joins-test/join-order-test]].

(defn- apply-joins-honey-sql-2
  [driver honeysql-form joins]
  (letfn [(append-joins [join-by]
            (into (vec join-by)
                  (mapcat (fn [{:keys [strategy], :as join}]
                            [strategy (join->honeysql driver join)]))
                  joins))]
    (update honeysql-form :join-by append-joins)))
(defmethod apply-top-level-clause [:sql :joins]
  [driver _ honeysql-form {:keys [joins]}]
  #_{:clj-kondo/ignore [:deprecated-var]}
  (let [f apply-joins-honey-sql-2]
    (f driver honeysql-form joins)))

---------------------------------------------------- order-by ----------------------------------------------------

(defmethod ->honeysql [:sql :asc]
  [driver [direction field]]
  [(->honeysql driver field) direction])
(defmethod ->honeysql [:sql :desc]
  [driver [direction field]]
  [(->honeysql driver field) direction])
(defmethod apply-top-level-clause [:sql :order-by]
  [driver _ honeysql-form {subclauses :order-by}]
  (reduce sql.helpers/order-by honeysql-form (mapv (partial ->honeysql driver) subclauses)))

-------------------------------------------------- limit & page --------------------------------------------------

(defmethod apply-top-level-clause [:sql :limit]
  [_driver _top-level-clause honeysql-form {value :limit}]
  (sql.helpers/limit honeysql-form (inline-num value)))
(defmethod apply-top-level-clause [:sql :page]
  [_driver _top-level-clause honeysql-form {{:keys [items page]} :page}]
  (-> honeysql-form
      (sql.helpers/limit (inline-num items))
      (sql.helpers/offset (inline-num (* items (dec page))))))

-------------------------------------------------- source-table --------------------------------------------------

(defn- has-to-honeysql-impl-for-legacy-table? [driver]
  (not (identical? (get-method ->honeysql [driver :model/Table])
                   (get-method ->honeysql [:sql :model/Table]))))
(defmethod ->honeysql [:sql :model/Table]
  [driver table]
  (sql.qp.deprecated/log-deprecation-warning
   driver
   "metabase.driver.sql.query-processor/->honeysql for metabase.models.table/Table or :model/Table"
   "0.48.0")
  (let [{table-name :name, schema :schema} table]
    (->honeysql driver (h2x/identifier :table schema table-name))))
(defmethod ->honeysql [:sql :metadata/table]
  [driver table]
  (if (has-to-honeysql-impl-for-legacy-table? driver)
    (do
      (sql.qp.deprecated/log-deprecation-warning
       driver
       "metabase.driver.sql.query-processor/->honeysql for metabase.models.table/Table or :model/Table"
       "0.48.0")
      (->honeysql driver #_{:clj-kondo/ignore [:deprecated-var]} (qp.store/->legacy-metadata table)))
    (let [{table-name :name, schema :schema} table]
      (->honeysql driver (h2x/identifier :table schema table-name)))))
(defmethod apply-top-level-clause [:sql :source-table]
  [driver _top-level-clause honeysql-form {source-table-id :source-table}]
  (let [table (lib.metadata/table (qp.store/metadata-provider) source-table-id)
        expr  (->honeysql driver table)]
    (sql.helpers/from honeysql-form [expr])))

+----------------------------------------------------------------------------------------------------------------+ | Building the HoneySQL Form | +----------------------------------------------------------------------------------------------------------------+

Order to apply top-level clauses in. This is important because we build things like the SELECT clause progressively and MBQL requires us to return results with :breakout columns before :aggregation, etc.

Map of clause -> index, e.g.

{:source-table 0, :breakout 1, ...}

(def ^:private top-level-clause-application-order
  (into {} (map-indexed
            #(vector %2 %1)
            [:source-table :breakout :aggregation :fields :filter :joins :order-by :page :limit])))

Return the keys present in an MBQL inner-query in the order they should be processed.

(defn- query->keys-in-application-order
  [inner-query]
  ;; sort first by any known top-level clauses according to the `top-level-application-clause-order` defined above,
  ;; then sort any unknown clauses by name.
  (sort-by (fn [clause] [(get top-level-clause-application-order clause Integer/MAX_VALUE) clause])
           (keys inner-query)))
(defn- format-honeysql-2 [driver dialect honeysql-form]
  ;; make sure [[driver/*driver*]] is bound, we need it for [[sqlize-value]]
  (binding [driver/*driver* driver]
    (if (map? honeysql-form)
      (sql/format honeysql-form {:dialect      dialect
                                 :quoted       true
                                 :quoted-snake false
                                 :inline       driver/*compile-with-inline-parameters*})
      ;; for weird cases when we want to compile just one particular snippet. Why are we doing this? Who knows. This seems
      ;; to not really be supported by Honey SQL 2, so hack around it for now. See upstream issue
      ;; https://github.com/seancorfield/honeysql/issues/456
      (binding [sql/*dialect*      (sql/get-dialect dialect)
                sql/*quoted*       true
                sql/*quoted-snake* false
                sql/*inline*       driver/*compile-with-inline-parameters*]
        (sql/format-expr honeysql-form {:nested true})))))

Compile honeysql-form to a [sql & args] vector. Prior to 0.51.0, this was a plain function, but was made a multimethod in 0.51.0 to support drivers that need to always specify [[metabase.driver/compile-with-inline-parameters]].

(defmulti format-honeysql
  {:arglists '([driver honeysql-form]), :added "0.51.0"}
  driver/dispatch-on-initialized-driver
  :hierarchy #'driver/hierarchy)
(defmethod format-honeysql :sql
  [driver honeysql-form]
  (let [dialect (quote-style driver)]
    (try
      (format-honeysql-2 driver dialect honeysql-form)
      (catch Throwable e
        (try
          (log/error e (u/format-color :red
                                       "Invalid HoneySQL form: %s\n%s"
                                       (ex-message e) (u/pprint-to-str honeysql-form)))
          (finally
            (throw (ex-info (tru "Error compiling HoneySQL form: {0}" (ex-message e))
                            {:dialect dialect
                             :form    honeysql-form
                             :type    qp.error-type/driver}
                            e))))))))
(defn- default-select [driver {[from] :from, :as _honeysql-form}]
  (let [table-identifier (if (sequential? from)
                           ;; Grab the alias part.
                           ;;
                           ;; Honey SQL 2 = [expr [alias]]
                           (first (second from))
                           from)
        [raw-identifier] (format-honeysql driver table-identifier)
        expr             (if (seq raw-identifier)
                           [:raw (format "%s.*" raw-identifier)]
                           :*)]
    [[expr]]))

Add SELECT * to honeysql-form if no :select clause is present.

(defn- add-default-select
  [driver {:keys [select select-top], :as honeysql-form}]
  ;; TODO - this is hacky -- we should ideally never need to add `SELECT *`, because we should know what fields to
  ;; expect from the source query, and middleware should be handling that for us
  (cond
    (and (empty? select)
         (empty? select-top))
    (assoc honeysql-form :select (default-select driver honeysql-form))
    ;; select-top currently only has the first arg, the limit
    (= (count select-top) 1)
    (update honeysql-form :select-top (fn [existing]
                                        (into existing (default-select driver honeysql-form))))
    :else
    honeysql-form))

apply-top-level-clause for all of the top-level clauses in inner-query, progressively building a HoneySQL form. Clauses are applied according to the order in top-level-clause-application-order.

(defn- apply-top-level-clauses
  ([driver honeysql-form inner-query]
   (apply-top-level-clauses driver honeysql-form inner-query identity))
  ([driver honeysql-form inner-query xform]
   (transduce
    xform
    (fn
      ([honeysql-form]
       (add-default-select driver honeysql-form))
      ([honeysql-form k]
       (apply-top-level-clause driver k honeysql-form inner-query)))
    honeysql-form
    (query->keys-in-application-order inner-query))))
(declare apply-clauses)

Handle a :source-query clause by adding a recursive SELECT or native query. If the source query has ambiguous column names, use a WITH statement to rename the source columns. At the time of this writing, all source queries are aliased as source.

(defn- apply-source-query
  [driver honeysql-form {{:keys [native params] persisted :persisted-info/native :as source-query} :source-query
                         source-metadata :source-metadata}]
  (let [table-alias (->honeysql driver (h2x/identifier :table-alias source-query-alias))
        source-clause (cond
                        persisted
                        (sql-source-query persisted nil)
                        native
                        (sql-source-query native params)
                        :else
                        (apply-clauses driver {} source-query))
        ;; TODO: Use MLv2 here to get source and desired-aliases
        alias-info (mapv (fn [{[_ desired-ref-name] :field_ref source-name :name}]
                           [source-name desired-ref-name])
                         source-metadata)
        source-aliases (mapv first alias-info)
        desired-aliases (mapv second alias-info)
        duplicate-source-aliases? (and (> (count source-aliases) 1)
                                       (not (apply distinct? source-aliases)))
        needs-columns? (and (seq desired-aliases)
                            (> (count desired-aliases) 1)
                            duplicate-source-aliases?
                            (apply distinct? desired-aliases)
                            (every? string? desired-aliases))]
    (merge
     honeysql-form
     (if needs-columns?
        ;; HoneySQL cannot expand [::h2x/identifier :table "source"] in the with alias.
        ;; This is ok since we control the alias.
       {:with [[[source-query-alias {:columns (mapv #(h2x/identifier :field %) desired-aliases)}]
                source-clause]]
        :from [[table-alias]]}
       {:from [[source-clause [table-alias]]]}))))

Like [[apply-top-level-clauses]], but handles source-query as well, which needs to be handled in a special way because it is aliased.

(defn- apply-clauses
  [driver honeysql-form {:keys [source-query], :as inner-query}]
  (binding [*inner-query* inner-query]
    (if source-query
      (apply-top-level-clauses
       driver
       (apply-source-query driver honeysql-form inner-query)
       inner-query
       ;; don't try to do anything with the source query recursively.
       (remove (partial = :source-query)))
      (apply-top-level-clauses driver honeysql-form inner-query))))

Do miscellaneous transformations to the MBQL before compiling the query. These changes are idempotent, so it is safe to use this function in your own implementations of [[driver/mbql->native]], if you want to apply changes to the same version of the query that we will ultimately be compiling.

(defmulti preprocess
  {:changelog-test/ignore true, :arglists '([driver inner-query]), :added "0.42.0"}
  driver/dispatch-on-initialized-driver
  :hierarchy #'driver/hierarchy)

This is a wrapper around [[qp.util.transformations.nest-breakouts/nest-breakouts-in-stages-with-window-aggregation]], which is written for pMBQL, so we can use it with a legacy inner query. Once we rework the SQL QP to use pMBQL we can remove this.

(mu/defn- nest-breakouts-in-queries-with-window-fn-aggregations :- mbql.s/MBQLQuery
  [inner-query :- mbql.s/MBQLQuery]
  (let [metadata-provider (qp.store/metadata-provider)
        database-id       (u/the-id (lib.metadata/database (qp.store/metadata-provider)))]
    (-> (lib.query/query-from-legacy-inner-query metadata-provider database-id inner-query)
        qp.util.transformations.nest-breakouts/nest-breakouts-in-stages-with-window-aggregation
        lib.convert/->legacy-MBQL
        :query)))

[[qp.util.transformations.nest-breakouts/nest-breakouts-in-stages-with-window-aggregation]] already does basically the same check, this is here mostly to avoid the performance hit of converting to pMBQL and back in queries that have no cumulative aggregations at all. Once we convert the SQL QP to pMBQL we can remove this.

(defn- has-window-function-aggregations? [inner-query]
  (or (lib.util.match/match (mapcat inner-query [:aggregation :expressions])
        #{:cum-sum :cum-count :offset}
        true)
      (when-let [source-query (:source-query inner-query)]
        (has-window-function-aggregations? source-query))))
(defn- maybe-nest-breakouts-in-queries-with-window-fn-aggregations
  [inner-query]
  (cond-> inner-query
    (has-window-function-aggregations? inner-query)
    nest-breakouts-in-queries-with-window-fn-aggregations))
(defmethod preprocess :sql
  [_driver inner-query]
  (-> inner-query
      maybe-nest-breakouts-in-queries-with-window-fn-aggregations
      add/add-alias-info
      nest-query/nest-expressions))
(mu/defn mbql->honeysql :- [:or :map [:tuple [:= :inline] :map]]
  "Build the HoneySQL form we will compile to SQL and execute."
  [driver               :- :keyword
   {inner-query :query} :- :map]
  (binding [driver/*driver* driver]
    (let [inner-query (preprocess driver inner-query)]
      (log/tracef "Compiling MBQL query\n%s" (u/pprint-to-str 'magenta inner-query))
      (u/prog1 (apply-clauses driver {} inner-query)
        (log/debugf "\nHoneySQL Form: %s\n%s" (u/emoji "🍯") (u/pprint-to-str 'cyan <>))
        (qp.debug/debug> (list '🍯 <>))))))

MBQL -> Native

(mu/defn mbql->native :- [:map
                          [:query  :string]
                          [:params [:maybe [:sequential :any]]]]
  "Transpile MBQL query into a native SQL statement. This is the `:sql` driver implementation
  of [[driver/mbql->native]] (actual multimethod definition is in [[metabase.driver.sql]]."
  [driver      :- :keyword
   outer-query :- :map]
  (let [honeysql-form (mbql->honeysql driver outer-query)
        [sql & args]  (format-honeysql driver honeysql-form)]
    {:query sql, :params args}))