diff options
| author | Tatsuo Ishii <ishii@postgresql.org> | 2025-10-03 09:47:36 +0900 |
|---|---|---|
| committer | Tatsuo Ishii <ishii@postgresql.org> | 2025-10-03 09:47:36 +0900 |
| commit | 25a30bbd4235a49c854036c84fe90f2bc5a87652 (patch) | |
| tree | 263bb113d48edb9858b6ad140590e9cec17a81d2 /src/backend/catalog | |
| parent | 381f5cffae0040a402e082adc5d5e7636035d2a7 (diff) | |
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 <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
Diffstat (limited to 'src/backend/catalog')
| -rw-r--r-- | src/backend/catalog/sql_features.txt | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/src/backend/catalog/sql_features.txt b/src/backend/catalog/sql_features.txt index ebe85337c28..3a8ad201607 100644 --- a/src/backend/catalog/sql_features.txt +++ b/src/backend/catalog/sql_features.txt @@ -518,7 +518,7 @@ T612 Advanced OLAP operations YES T613 Sampling YES T614 NTILE function YES T615 LEAD and LAG functions YES -T616 Null treatment option for LEAD and LAG functions NO +T616 Null treatment option for LEAD and LAG functions YES T617 FIRST_VALUE and LAST_VALUE functions YES T618 NTH_VALUE function NO function exists, but some options missing T619 Nested window functions NO |