postgresql/doc
Tom Lane d3a4f89d8a Allow no-op GiST support functions to be omitted.
There are common use-cases in which the compress and/or decompress
functions can be omitted, with the result being that we make no
data transformation when storing or retrieving index values.
Previously, you had to provide a no-op function anyway, but this
patch allows such opclass support functions to be omitted.

Furthermore, if the compress function is omitted, then the core code
knows that the stored representation is the same as the original data.
This means we can allow index-only scans without requiring a fetch
function to be provided either.  Previously you had to provide a
no-op fetch function if you wanted IOS to work.

This reportedly provides a small performance benefit in such cases,
but IMO the real reason for doing it is just to reduce the amount of
useless boilerplate code that has to be written for GiST opclasses.

Andrey Borodin, reviewed by Dmitriy Sarafannikov

Discussion: https://postgr.es/m/CAJEAwVELVx9gYscpE=Be6iJxvdW5unZ_LkcAaVNSeOwvdwtD=A@mail.gmail.com
2017-09-19 23:32:59 -04:00
..
src Allow no-op GiST support functions to be omitted. 2017-09-19 23:32:59 -04:00
bug.template Stamp HEAD as 11devel. 2017-08-14 18:08:30 -04:00
KNOWN_BUGS Remove extra newlines at end and beginning of files, add missing newlines 2010-08-19 05:57:36 +00:00
Makefile Remove maintainer-check target, fold into normal build 2013-10-10 20:11:56 -04:00
MISSING_FEATURES Remove extra newlines at end and beginning of files, add missing newlines 2010-08-19 05:57:36 +00:00
TODO Change documentation references to PG website to use https: not http: 2017-05-20 21:50:47 -04:00