metabase.driver.sql.query-processor — metabase-core 1.0.0-SNAPSHOT

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

*nested-query-level* clj

How many levels deep are we into nested queries? (0 = top level.) We keep track of this so we know what level to find referenced aggregations (otherwise something like [:aggregation 0] could be ambiguous in a nested query). Each nested query increments this counter by 1.

*query* clj

The outer query currently being processed. (This is only used to power [:aggregation <index>] and expression references, because they need to be able to find the corresponding clauses outside of where they're being processed.)

*table-alias* clj

The alias, if any, that should be used to qualify Fields when building the HoneySQL form, instead of defaulting to schema + Table name. Used to implement things like :joined-fields.

->honeysql clj multimethod

(->honeysql driver x)

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.

apply-top-level-clause clj multimethod

(apply-top-level-clause driver top-level-clause honeysql-form query)

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).

as clj

(as driver field-clause)

(as driver field-clause unique-name-fn)

Generate HoneySQL for an AS form (e.g. <form> AS <field>) using the name information of a field-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 unwrapped field literals, this returns the form as-is.

(as [:field-literal "x" :type/Text]) ;; -> <compiled-form> ;; -> SELECT "x"

(as [:datetime-field [:field-literal "x" :type/Text] :month]) ;; -> [<compiled-form> :x] ;; -> SELECT date_extract("x", 'month') AS "x"

As with field-clause->alias, you can pass a unique-name-fn to generate unique names for a sequence of aliases, such as for a SELECT clause.

build-honeysql-form clj

(build-honeysql-form driver {inner-query :query})

Inputs: [driver {inner-query :query} :- su/Map]

Build the HoneySQL form we will compile to SQL and execute.

cast-unix-timestamp-field-if-needed clj

(cast-unix-timestamp-field-if-needed driver field field-identifier)

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

current-datetime-fn clj multimethod

(current-datetime-fn driver)

HoneySQL form that should be used to get the current datetime (or equivalent). Defaults to :%now.

date clj multimethod

(date driver unit field-or-value)

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

field->alias clj multimethod

(field->alias driver field)

Return the string alias that should be used to for field, an instance of the Field model, i.e. in an AS clause. The default implementation calls :name, which returns the unqualified name of the Field.

Return nil to prevent field from being aliased.

field->identifier clj multimethod

(field->identifier driver field)

Return a HoneySQL form that should be used as the identifier for field, an instance of the Field model. The default implementation returns a keyword generated by from the components returned by field/qualified-name-components. Other drivers like BigQuery need to do additional qualification, e.g. the dataset name as well. (At the time of this writing, this is only used by the SQL parameters implementation; in the future it will probably be used in more places as well.)

field-clause->alias clj

(field-clause->alias driver field-clause)

(field-clause->alias driver field-clause unique-name-fn)

Inputs: ([driver field-clause] [driver field-clause :- mbql.s/Field unique-name-fn :- (s/pred fn?)])

Generate HoneySQL for an approriate alias (e.g., for use with SQL AN) for a Field clause of any type, or nil if the Field should not be aliased (e.g. if field->alias returns nil).

Optionally pass a state-maintaining unique-name-fn, such as mbql.u/unique-name-generator, to guarantee that each alias generated is unique when generating a sequence of aliases, such as for a SELECT clause.

honeysql-form->sql+args clj

(honeysql-form->sql+args driver honeysql-form)

Inputs: [driver honeysql-form :- su/Map]

Convert honeysql-form to a vector of SQL string and params, like you'd pass to JDBC.

join->honeysql clj multimethod

(join->honeysql driver join)

Compile a single MBQL join to HoneySQL.

join-source clj multimethod

(join-source driver join)

Generate HoneySQL for a table or query to be joined.

mbql->native clj

(mbql->native driver {inner-query :query database :database :as outer-query})

Transpile MBQL query into a native SQL statement.

quote-style clj multimethod

(quote-style driver)

Return the quoting style that should be used by HoneySQL when building a SQL statement. Defaults to :ansi, but other valid options are :mysql, :sqlserver, :oracle, and :h2 (added in metabase.util.honeysql-extensions; like :ansi, but uppercases the result).

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

source-query-alias clj

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

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

unix-timestamp->timestamp clj multimethod

(unix-timestamp->timestamp driver seconds-or-milliseconds field-or-value)

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).