On Thu, Jun 1, 2017 at 4:10 PM, Alexander Korotkov < a.korot...@postgrespro.ru> wrote:
> On Wed, May 31, 2017 at 7:18 PM, Alexander Korotkov < > a.korot...@postgrespro.ru> wrote: > >> On Wed, May 31, 2017 at 6:53 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: >> >>> Alexander Korotkov <a.korot...@postgrespro.ru> writes: >>> > I've discovered that PostgreSQL is able to run following kind of >>> queries in >>> > order to change statistic-gathering target for an indexed expression. >>> >>> > ALTER INDEX index_name ALTER COLUMN expr SET STATISTICS stat_target; >>> >>> > It's been previously discussed in [1]. >>> >>> > I think this should be fixed not just in docs. This is why I've >>> started >>> > thread in pgsql-hackers. For me usage of internal column names "expr", >>> > "expr1", "expr2" etc. looks weird. And I think we should replace it >>> with a >>> > better syntax. What do you think about these options? >>> >>> > ALTER INDEX index_name ALTER EXPRESSION 0 SET STATISTICS stat_target; >>> -- >>> > Refer expression by its number >>> > ALTER INDEX index_name ALTER EXPRESSION (x + y) SET STATISTICS >>> stat_target; >>> > -- Refer expression by its definition >>> >>> Don't like either of those particularly, but what about just targeting >>> a column by column number, independently of whether it's an expression? >>> >>> ALTER INDEX myindex ALTER COLUMN 4 SET STATISTICS 1000; >>> >> >> I completely agree with that. >> If no objections, I will write a patch for that. >> > > Please, find it in attached patch. > > I decided to forbid referencing columns by numbers for tables, because > those numbers could contain gaps. Also, I forbid altering statistics > target for non-expression index columns, because it has no effect. > Patch rebased to current master is attached. ------ Alexander Korotkov Postgres Professional: http://www.postgrespro.com The Russian Postgres Company
alter-index-statistics-2.patch
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