From 25a30bbd4235a49c854036c84fe90f2bc5a87652 Mon Sep 17 00:00:00 2001 From: Tatsuo Ishii Date: Fri, 3 Oct 2025 09:47:36 +0900 Subject: Add IGNORE NULLS/RESPECT NULLS option to Window functions. Add IGNORE NULLS/RESPECT NULLS option (null treatment clause) to lead, lag, first_value, last_value and nth_value window functions. If unspecified, the default is RESPECT NULLS which includes NULL values in any result calculation. IGNORE NULLS ignores NULL values. Built-in window functions are modified to call new API WinCheckAndInitializeNullTreatment() to indicate whether they accept IGNORE NULLS/RESPECT NULLS option or not (the API can be called by user defined window functions as well). If WinGetFuncArgInPartition's allowNullTreatment argument is true and IGNORE NULLS option is given, WinGetFuncArgInPartition() or WinGetFuncArgInFrame() will return evaluated function's argument expression on specified non NULL row (if it exists) in the partition or the frame. When IGNORE NULLS option is given, window functions need to visit and evaluate same rows over and over again to look for non null rows. To mitigate the issue, 2-bit not null information array is created while executing window functions to remember whether the row has been already evaluated to NULL or NOT NULL. If already evaluated, we could skip the evaluation work, thus we could get better performance. Author: Oliver Ford Co-authored-by: Tatsuo Ishii Reviewed-by: Krasiyan Andreev Reviewed-by: Andrew Gierth Reviewed-by: Tom Lane Reviewed-by: David Fetter Reviewed-by: Vik Fearing Reviewed-by: "David G. Johnston" Reviewed-by: Chao Li Discussion: https://postgr.es/m/flat/CAGMVOdsbtRwE_4+v8zjH1d9xfovDeQAGLkP_B6k69_VoFEgX-A@mail.gmail.com --- src/backend/parser/gram.y | 19 ++++++++++++++----- src/backend/parser/parse_func.c | 9 +++++++++ 2 files changed, 23 insertions(+), 5 deletions(-) (limited to 'src/backend/parser') diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y index f1def67ac7c..57bf7a7c7f2 100644 --- a/src/backend/parser/gram.y +++ b/src/backend/parser/gram.y @@ -632,7 +632,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query); %type window_clause window_definition_list opt_partition_clause %type window_definition over_clause window_specification opt_frame_clause frame_extent frame_bound -%type opt_window_exclusion_clause +%type null_treatment opt_window_exclusion_clause %type opt_existing_window_name %type opt_if_not_exists %type opt_unique_null_treatment @@ -730,7 +730,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query); HANDLER HAVING HEADER_P HOLD HOUR_P - IDENTITY_P IF_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE + IDENTITY_P IF_P IGNORE_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE INCLUDING INCREMENT INDENT INDEX INDEXES INHERIT INHERITS INITIALLY INLINE_P INNER_P INOUT INPUT_P INSENSITIVE INSERT INSTEAD INT_P INTEGER INTERSECT INTERVAL INTO INVOKER IS ISNULL ISOLATION @@ -765,7 +765,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query); RANGE READ REAL REASSIGN RECURSIVE REF_P REFERENCES REFERENCING REFRESH REINDEX RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA - RESET RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP + RESET RESPECT_P RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP ROUTINE ROUTINES ROW ROWS RULE SAVEPOINT SCALAR SCHEMA SCHEMAS SCROLL SEARCH SECOND_P SECURITY SELECT @@ -15805,7 +15805,7 @@ func_application: func_name '(' ')' * (Note that many of the special SQL functions wouldn't actually make any * sense as functional index entries, but we ignore that consideration here.) */ -func_expr: func_application within_group_clause filter_clause over_clause +func_expr: func_application within_group_clause filter_clause null_treatment over_clause { FuncCall *n = (FuncCall *) $1; @@ -15838,7 +15838,8 @@ func_expr: func_application within_group_clause filter_clause over_clause n->agg_within_group = true; } n->agg_filter = $3; - n->over = $4; + n->ignore_nulls = $4; + n->over = $5; $$ = (Node *) n; } | json_aggregate_func filter_clause over_clause @@ -16434,6 +16435,12 @@ filter_clause: /* * Window Definitions */ +null_treatment: + IGNORE_P NULLS_P { $$ = PARSER_IGNORE_NULLS; } + | RESPECT_P NULLS_P { $$ = PARSER_RESPECT_NULLS; } + | /*EMPTY*/ { $$ = NO_NULLTREATMENT; } + ; + window_clause: WINDOW window_definition_list { $$ = $2; } | /*EMPTY*/ { $$ = NIL; } @@ -17861,6 +17868,7 @@ unreserved_keyword: | HOUR_P | IDENTITY_P | IF_P + | IGNORE_P | IMMEDIATE | IMMUTABLE | IMPLICIT_P @@ -17979,6 +17987,7 @@ unreserved_keyword: | REPLACE | REPLICA | RESET + | RESPECT_P | RESTART | RESTRICT | RETURN diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c index c43020a769d..778d69c6f3c 100644 --- a/src/backend/parser/parse_func.c +++ b/src/backend/parser/parse_func.c @@ -100,6 +100,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs, bool agg_star = (fn ? fn->agg_star : false); bool agg_distinct = (fn ? fn->agg_distinct : false); bool func_variadic = (fn ? fn->func_variadic : false); + int ignore_nulls = (fn ? fn->ignore_nulls : NO_NULLTREATMENT); CoercionForm funcformat = (fn ? fn->funcformat : COERCE_EXPLICIT_CALL); bool could_be_projection; Oid rettype; @@ -518,6 +519,13 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs, errmsg("%s is not an ordered-set aggregate, so it cannot have WITHIN GROUP", NameListToString(funcname)), parser_errposition(pstate, location))); + + /* It also can't treat nulls as a window function */ + if (ignore_nulls != NO_NULLTREATMENT) + ereport(ERROR, + (errcode(ERRCODE_WRONG_OBJECT_TYPE), + errmsg("aggregate functions do not accept RESPECT/IGNORE NULLS"), + parser_errposition(pstate, location))); } } else if (fdresult == FUNCDETAIL_WINDOWFUNC) @@ -840,6 +848,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs, wfunc->winstar = agg_star; wfunc->winagg = (fdresult == FUNCDETAIL_AGGREGATE); wfunc->aggfilter = agg_filter; + wfunc->ignore_nulls = ignore_nulls; wfunc->runCondition = NIL; wfunc->location = location; -- cgit v1.2.3