Hash

memory

{"description":"Hash-join execution can partition work into batches backed by temporary files. This describes hash-join batching, not the spill policy of aggregate or Memoize nodes.","evidence":[{"archive_sha256":"555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f","label":"src/backend/executor/nodeHash.c","path":"src/backend/executor/nodeHash.c","sha256":"f83e9b10129450f2dc52ac7ea5147b7c51c12648ae1b3b3195bb3f0b4895fafc","url":"https://ftp.postgresql.org/pub/source/v18.6/postgresql-18.6.tar.bz2"},{"archive_sha256":"555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f","label":"src/backend/executor/nodeHashjoin.c","path":"src/backend/executor/nodeHashjoin.c","sha256":"4a72b0db253c1905c415462cfe56a2327ac65507c607b6d699d2717fa624ad56","url":"https://ftp.postgresql.org/pub/source/v18.6/postgresql-18.6.tar.bz2"}],"mechanism":"hash-batches","source_notes":["It's time to begin hashing, or if we just arrived here then hashing is already underway, so join in that effort. While hashing we have to be prepared to help increase the number of batches or buckets at any time, and if we arrived here when that was already underway we'll have to help complete that work immediately so that it's safe to access batches and buckets below.","Make sure that any tuples we wrote to disk are visible to others before anyone tries to load them.","Elect one backend to disable any further growth. Batches are now fixed. While building them we made sure they'd fit in our memory budget when we load them back in later (or we tried to do that and gave up because we detected extreme skew).","Parallel Hash tries to use the combined hash_mem of all workers to avoid the need to batch. If that won't work, it falls back to hash_mem per worker and tries to process batches in parallel."]}

source inventory

{"executor":"src/backend/executor/execProcnode.c","explain":"src/backend/commands/explain.c","implementation":"src/backend/executor/nodeHash.c"}