Re: Index Onlys Scan for expressions - Mailing list pgsql-hackers

From Vladimir Sitnikov
Subject Re: Index Onlys Scan for expressions
Date
Msg-id CAB=Je-FroJAi-v8PeuDX3xW0JC8Y6RrD=bfg3uzqeOjd6zHuuw@mail.gmail.com
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In response to Re: Index Onlys Scan for expressions  (Ildar Musin <i.musin@postgrespro.ru>)
Responses Re: Index Onlys Scan for expressions  (Robert Haas <robertmhaas@gmail.com>)
List pgsql-hackers
Ildar> Could you please try the patch and tell if it works for you?

I've tested patch6 against recent head. The patch applies with no problems.

The previous case (filter on top of i-o-s) is fixed. Great work.


However, it looks there are issues when accessing non-indexed columns.
The error is "ERROR: variable not found in subplan target list"
The case is 02_case2_fails.sql (see the gist link above)

The essence of the case is "create index on substr(vc, 1, 128)"
and assume that majority of the rows have length(vc)<128.
Under that conditions, it would be nice to do index-only-scan
and filter (like in my previous case), but detect "long" rows
and do additional recheck for them.

Vladimir

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