Parallel hash joins pool worker memory to build one shared table instead of having each worker build its own copy—a distinction that matters enormously on…
The third way to use an index, after the plain index scan and bitmap scan of enable_indexscan and enable_bitmapscan — and the one with the most-misunderstood ca
PostgreSQL 13 made hash aggregation memory-safe by allowing it to spill to disk — but that safety introduced a surprise regression for some queries on upgrade.
Parallel hash joins pool worker memory to build one shared table instead of having each worker build its own copy—a distinction that matters enormously on…
Parallel Append spreads workers across partitions or UNION branches simultaneously, not sequentially.
Nested loop joins are PostgreSQL's most notorious performance disaster—but only when the planner misestimates row counts.
Merge join shines when data is already sorted by an index, but stumbles when it has to pay for a sort first.
Materialize buffers rows unconditionally; Memoize caches them by key. Same goal, opposite mechanisms—and both deserve a closer look.
The third way to use an index, after the plain index scan and bitmap scan of enable_indexscan and enable_bitmapscan — and the one with the most-misunderstood ca
Incremental sort exploits presorted data to avoid expensive full sorts, but cost estimation errors on skewed data can backfire.
Diagnose spilling hash joins with `enable_hashjoin = off`.
PostgreSQL 13 made hash aggregation memory-safe by allowing it to spill to disk — but that safety introduced a surprise regression for some queries on upgrade.
Learn relational algebra by building expressions that compile to real SQL.