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/parse_func.c | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'src/backend/parser/parse_func.c') 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