Hi Ildar,I've looked at this patch again today to do a bit more thorough review, and I think it's fine. There are a few comments (particularly in the new code in check_index_only) that need improving, and also a few small tweaks in the walkers.
Attached is a modified v5 patch with the proposed changes - it's probably easier than explaining what the changes should/might be.
I've added an XXX comment in check_index_only_expr_walker - ISTM we're first explicitly matching Vars to index attributes, and then dealing with expressions. But we loop over all index columns (including those that can only really match Vars). Not sure if it makes any difference, but is it worth differentiating between Var and non-Var expressions? Why not to simply call match_index_to_operand() in both cases?
I've also tweaked a few comments to match project code style, and moved a few variables into the block where they are used. But the latter is probably matter of personal taste, I guess.
regards -- Tomas Vondra http://www.2ndQuadrant.com PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
indexonlyscan5-tomas.patch
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