This is cont'd from CF3. http://www.postgresql.org/message-id/20131122.165927.27412386.horiguchi.kyotaro@lab.ntt.co.jp The issue in brief is that UNION is never flattened differently to UNION ALL so UNION cannot make use of index scan even if usable. This patch flattens UNION likewise currently did for UNION ALL. This patch needs another 'UNION ALL' patch and further gain with even another 'Widening application of indices' patch. ('Ready for Commit' now in CF3..) http://www.postgresql.org/message-id/20140114.180447.145186052.horiguchi.kyotaro@lab.ntt.co.jp http://www.postgresql.org/message-id/20140114.180810.122352231.horiguchi.kyotaro@lab.ntt.co.jp You can see the detailed outlines in the message at here, http://www.postgresql.org/message-id/20131031.194251.12577697.horiguchi.kyotaro@lab.ntt.co.jp The attached patche is rebased to current 9.4dev HEAD and make check at the topmost directory and src/test/isolation are passed without error. regards, -- Kyotaro Horiguchi NTT Open Source Software Center
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