Struct Function

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pub struct Function { /* private fields */ }

Expand description

A PostgreSQL function call, with every decoration the grammar hangs off one.

From PostgreSQL 17, 4.2.7 Aggregate Expressions and 4.2.8 Window Function Calls:

name ( [ DISTINCT ] expression [, ...] [ ORDER BY … ] ) [ FILTER ( WHERE … ) ]
name ( expression [, ...] ) WITHIN GROUP ( ORDER BY … ) [ FILTER ( WHERE … ) ]
name ( … ) [ FILTER ( WHERE … ) ] OVER ( window_definition | window_name )

plus the FROM-list form, where a set-returning function may name its result columns:

function_name ( … ) [ AS ] [ alias ] ( column_definition [, ...] )

Expr::Func carries only what all three dialects share, so everything above lives here and reaches core through Expr::Custom — which is why this is a keelson-psql type and not a core one.

use keelson_psql::{f, quote, window};

// avg("views") OVER (PARTITION BY "user_id")
let e = f("avg", quote("views")).over(window::partition_by(quote("user_id")));

Implementations§

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impl Function

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pub fn new( name: impl Into<Cow<'static, str>>, args: impl IntoExprList, ) -> Function

A call to name with args.

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pub fn distinct(self) -> Function

DISTINCT, for an aggregate that should see each distinct input once.

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pub fn order_by(self, order: impl IntoExpr) -> Function

Add a sort key to the aggregate’s own ORDER BY.

Rendered inside the argument list — array_agg(x ORDER BY y) — unless within_group moved it out.

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pub fn within_group(self) -> Function

Write the ORDER BY as WITHIN GROUP (ORDER BY …), which is what an ordered-set aggregate such as percentile_cont requires.

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pub fn filter(self, condition: impl IntoExpr) -> Function

Add a condition to FILTER (WHERE …). Several are AND-joined.

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pub fn as_table(self, alias: impl Into<Cow<'static, str>>) -> TableFunction

The alias of a set-returning function used as a from-item: f() AS "t", or — with columns — f() AS "t" ("a" int).

Not the select-list alias — that is as_. The two must not meet: gram.y’s func_alias_clause shares one AS between the alias and the column definitions, so a second alias would be a second AS, which is a syntax error. That is why this returns a TableFunction, on which as_ — and the rest of the expression-position decorations — does not exist.

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pub fn columns<N, T>( self, columns: impl IntoIterator<Item = (N, T)>, ) -> TableFunction
where N: Into<Cow<'static, str>>, T: Into<Cow<'static, str>>,

Name and type the columns a set-returning function returns: json_to_recordset($1) AS ("a" int, "b" text).

The name is quoted; the type is written verbatim, so int, text[] and numeric(10, 2) all work.

Returns a TableFunction for the same reason as_table does: the column definitions spend the one AS the func_alias_clause production has, so the select-list as_ cannot be allowed to write another.

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pub fn over(self, mods: impl Mod<Window>) -> Expr

Attach OVER (…), built from window mods — psql::window::* and psql::frame::*.

Ends the builder, because OVER is the last thing in the grammar: it is written after FILTER, and nothing may follow it. over(()) gives the legal OVER (), which means the whole partition.

To reference a window declared in the statement’s WINDOW clause, use over_name — not over(window::based_on(..)), which is the copying form and cannot copy a frame.

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