Re: pgsql: Improve handling of NULLs in KNN-GiST and KNN-SP-GiST

hello admin

is there any issue with the mail list system? can be improved?  I usually receive multi times on the same thread, such as this one, attached for the screen dump.

sorry for interruption and inconveniences

best regards

Tony

On 2019/9/20 03:11, Alexander Korotkov wrote:

Improve handling of NULLs in KNN-GiST and KNN-SP-GiST

This commit improves subject in two ways:

* It removes ugliness of 02f90879e7, which stores distance values and null
flags in two separate arrays after GISTSearchItem struct. Instead we pack
both distance value and null flag in IndexOrderByDistance struct. Alignment
overhead should be negligible, because we typically deal with at most few
"col op const" expressions in ORDER BY clause.
* It fixes handling of "col op NULL" expression in KNN-SP-GiST. Now, these
expression are not passed to support functions, which can't deal with them.
Instead, NULL result is implicitly assumed. It future we may decide to
teach support functions to deal with NULL arguments, but current solution is
bugfix suitable for backpatch.

Reported-by: Nikita Glukhov
Discussion: https://postgr.es/m/826f57ee-afc7-8977-c44c-6111d18b02ec%40postgrespro.ru
Author: Nikita Glukhov
Reviewed-by: Alexander Korotkov
Backpatch-through: 9.4

Branch
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REL9_6_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/53d9cf2db5ded873fbcc031acb584a2c05e4983b

Modified Files
--------------
src/backend/access/gist/gistget.c | 75 ++++++++++++++------------------------
src/backend/access/gist/gistscan.c | 16 +++-----
src/include/access/genam.h | 7 ++++
src/include/access/gist_private.h | 27 +++-----------
src/tools/pgindent/typedefs.list | 1 +
5 files changed, 47 insertions(+), 79 deletions(-)