Optimize multi-batch hash joins when the outer relation has a nonuniform
Tom Lane <tgl@sss.pgh.pa.us>
Optimize multi-batch hash joins when the outer relation has a nonuniform distribution, by creating a special fast path for the (first few) most common values of the outer relation. Tuples having hashvalues matching the MCVs are effectively forced to be in the first batch, so that we never write them out to the batch temp files. Bryce Cutt and Ramon Lawrence, with some editorialization by me.
Files
| Path | Change | +/− |
|---|---|---|
| src/backend/executor/nodeHash.c | modified | +435 −10 |
| src/backend/executor/nodeHashjoin.c | modified | +24 −5 |
| src/backend/nodes/copyfuncs.c | modified | +5 −1 |
| src/backend/nodes/outfuncs.c | modified | +6 −1 |
| src/backend/optimizer/path/costsize.c | modified | +15 −3 |
| src/backend/optimizer/plan/createplan.c | modified | +58 −4 |
| src/include/executor/hashjoin.h | modified | +39 −1 |
| src/include/executor/nodeHash.h | modified | +5 −3 |
| src/include/nodes/execnodes.h | modified | +6 −4 |
| src/include/nodes/plannodes.h | modified | +11 −2 |