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Add IGNORE NULLS/RESPECT NULLS option to Window functions.

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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 <ojford@gmail.com>
Co-authored-by: Tatsuo Ishii <ishii@postgresql.org>
Reviewed-by: Krasiyan Andreev <krasiyan@gmail.com>
Reviewed-by: Andrew Gierth <andrew@tao11.riddles.org.uk>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Reviewed-by: David Fetter <david@fetter.org>
Reviewed-by: Vik Fearing <vik@postgresfriends.org>
Reviewed-by: "David G. Johnston" <david.g.johnston@gmail.com>
Reviewed-by: Chao Li <lic@highgo.com>
Discussion: https://postgr.es/m/flat/CAGMVOdsbtRwE_4+v8zjH1d9xfovDeQAGLkP_B6k69_VoFEgX-A@mail.gmail.com
This commit is contained in:
Tatsuo Ishii
2025-10-03 09:47:36 +09:00
parent 381f5cffae
commit 25a30bbd42
15 changed files with 1092 additions and 61 deletions
Download Patch File Download Diff File Expand all files Collapse all files

19
src/backend/parser/gram.y
View File

@@ -632,7 +632,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
%type <list> window_clause window_definition_list opt_partition_clause
%type <windef> window_definition over_clause window_specification
opt_frame_clause frame_extent frame_bound
%type <ival> opt_window_exclusion_clause
%type <ival> null_treatment opt_window_exclusion_clause
%type <str> opt_existing_window_name
%type <boolean> opt_if_not_exists
%type <boolean> 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

9
src/backend/parser/parse_func.c
View File

@@ -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;