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25a30bbd42
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
71 lines
2.5 KiB
C
71 lines
2.5 KiB
C
/*-------------------------------------------------------------------------
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*
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* windowapi.h
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* API for window functions to extract data from their window
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*
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* A window function does not receive its arguments in the normal way
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* (and therefore the concept of strictness is irrelevant). Instead it
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* receives a "WindowObject", which it can fetch with PG_WINDOW_OBJECT()
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* (note V1 calling convention must be used). Correct call context can
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* be tested with WindowObjectIsValid(). Although argument values are
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* not passed, the call is correctly set up so that PG_NARGS() can be
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* used and argument type information can be obtained with
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* get_fn_expr_argtype(), get_fn_expr_arg_stable(), etc.
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*
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* Operations on the WindowObject allow the window function to find out
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* the current row number, total number of rows in the partition, etc
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* and to evaluate its argument expression(s) at various rows in the
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* window partition. See the header comments for each WindowObject API
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* function in nodeWindowAgg.c for details.
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*
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*
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* Portions Copyright (c) 2000-2025, PostgreSQL Global Development Group
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*
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* src/include/windowapi.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef WINDOWAPI_H
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#define WINDOWAPI_H
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#include "fmgr.h"
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/* values of "seektype" */
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#define WINDOW_SEEK_CURRENT 0
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#define WINDOW_SEEK_HEAD 1
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#define WINDOW_SEEK_TAIL 2
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/* this struct is private in nodeWindowAgg.c */
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typedef struct WindowObjectData *WindowObject;
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#define PG_WINDOW_OBJECT() ((WindowObject) fcinfo->context)
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#define WindowObjectIsValid(winobj) \
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((winobj) != NULL && IsA(winobj, WindowObjectData))
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extern void WinCheckAndInitializeNullTreatment(WindowObject winobj,
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bool allowNullTreatment,
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FunctionCallInfo fcinfo);
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extern void *WinGetPartitionLocalMemory(WindowObject winobj, Size sz);
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extern int64 WinGetCurrentPosition(WindowObject winobj);
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extern int64 WinGetPartitionRowCount(WindowObject winobj);
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extern void WinSetMarkPosition(WindowObject winobj, int64 markpos);
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extern bool WinRowsArePeers(WindowObject winobj, int64 pos1, int64 pos2);
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extern Datum WinGetFuncArgInPartition(WindowObject winobj, int argno,
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int relpos, int seektype, bool set_mark,
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bool *isnull, bool *isout);
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extern Datum WinGetFuncArgInFrame(WindowObject winobj, int argno,
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int relpos, int seektype, bool set_mark,
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bool *isnull, bool *isout);
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extern Datum WinGetFuncArgCurrent(WindowObject winobj, int argno,
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bool *isnull);
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#endif /* WINDOWAPI_H */
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