On Tue, Apr 18, 2023 at 5:07 PM Richard Guo <guofengli...@gmail.com> wrote:
> In thread [1] which discussed 'Right Anti Join', Tom once mentioned > 'Right Semi Join'. After a preliminary investigation I think it is > beneficial and can be implemented with very short change. With 'Right > Semi Join', what we want to do is to just have the first match for each > inner tuple. For HashJoin, after scanning the hash bucket for matches > to current outer, we just need to check whether the inner tuple has been > set match and skip it if so. For MergeJoin, we can do it by avoiding > restoring inner scan to the marked tuple in EXEC_MJ_TESTOUTER, in the > case when new outer tuple == marked tuple. > > As that thread is already too long, fork a new thread and attach a patch > used for discussion. The patch implements 'Right Semi Join' for > HashJoin. > The cfbot reminds that this patch does not apply any more, so rebase it to v2. Thanks Richard
v2-0001-Support-Right-Semi-Join-plan-shapes.patch
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