# Query Tuning

> Complete dossiers for 55 core PostgreSQL settings in Query Tuning.
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Dossier URLs remain flat; this category exists only to organize browsing and the sidebar.

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Section pages:

- [constraint_exclusion](/parameters/constraint-exclusion/): constraint_exclusion — Enables the planner to use constraints to optimize queries. Observed in PG9.0–19 Beta 3; its last measured boot default is partition in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [cpu_index_tuple_cost](/parameters/cpu-index-tuple-cost/): cpu_index_tuple_cost — Sets the planner's estimate of the cost of processing each index entry during an index scan. Observed in PG9.0–19 Beta 3; its last measured boot default is 0.005 in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [cpu_operator_cost](/parameters/cpu-operator-cost/): cpu_operator_cost — Sets the planner's estimate of the cost of processing each operator or function call. Observed in PG9.0–19 Beta 3; its last measured boot default is 0.0025 in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [cpu_tuple_cost](/parameters/cpu-tuple-cost/): cpu_tuple_cost — Sets the planner's estimate of the cost of processing each tuple (row). Observed in PG9.0–19 Beta 3; its last measured boot default is 0.01 in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [cursor_tuple_fraction](/parameters/cursor-tuple-fraction/): cursor_tuple_fraction — Sets the planner's estimate of the fraction of a cursor's rows that will be retrieved. Observed in PG9.0–19 Beta 3; its last measured boot default is 0.1 in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [default_statistics_target](/parameters/default-statistics-target/): Sets the default detail level for column statistics collected by ANALYZE when a column has no explicit target. More detail can improve cardinality estimates at the cost of collection time and catalog space.
- [effective_cache_size](/parameters/effective-cache-size/): A planner estimate of how much PostgreSQL data cache is effectively available to one query; it changes plan costing but allocates no memory.
- [enable_async_append](/parameters/enable-async-append/): enable_async_append — Enables the planner's use of async append plans. Observed in PG14–19 Beta 3; its last measured boot default is on in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [enable_bitmapscan](/parameters/enable-bitmapscan/): enable_bitmapscan — Enables the planner's use of bitmap-scan plans. Observed in PG9.0–19 Beta 3; its last measured boot default is on in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [enable_distinct_reordering](/parameters/enable-distinct-reordering/): enable_distinct_reordering — Enables reordering of DISTINCT keys. Observed in PG18–19 Beta 3; its last measured boot default is on in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [enable_eager_aggregate](/parameters/enable-eager-aggregate/): enable_eager_aggregate — Enables eager aggregation. Observed in PG19 Beta 3; its last measured boot default is on in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [enable_gathermerge](/parameters/enable-gathermerge/): enable_gathermerge — Enables the planner's use of gather merge plans. Observed in PG10–19 Beta 3; its last measured boot default is on in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [enable_group_by_reordering](/parameters/enable-group-by-reordering/): enable_group_by_reordering — Enables reordering of GROUP BY keys. Observed in PG17–19 Beta 3; its last measured boot default is on in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [enable_hashagg](/parameters/enable-hashagg/): enable_hashagg — Enables the planner's use of hashed aggregation plans. Observed in PG9.0–19 Beta 3; its last measured boot default is on in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [enable_hashjoin](/parameters/enable-hashjoin/): enable_hashjoin — Enables the planner's use of hash join plans. Observed in PG9.0–19 Beta 3; its last measured boot default is on in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [enable_incremental_sort](/parameters/enable-incremental-sort/): enable_incremental_sort — Enables the planner's use of incremental sort steps. Observed in PG13–19 Beta 3; its last measured boot default is on in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [enable_indexonlyscan](/parameters/enable-indexonlyscan/): enable_indexonlyscan — Enables the planner's use of index-only-scan plans. Observed in PG9.2–19 Beta 3; its last measured boot default is on in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [enable_indexscan](/parameters/enable-indexscan/): enable_indexscan — Enables the planner's use of index-scan plans. Observed in PG9.0–19 Beta 3; its last measured boot default is on in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [enable_material](/parameters/enable-material/): enable_material — Enables the planner's use of materialization. Observed in PG9.0–19 Beta 3; its last measured boot default is on in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [enable_memoize](/parameters/enable-memoize/): enable_memoize — Enables the planner's use of memoization. Observed in PG14–19 Beta 3; its last measured boot default is on in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [enable_mergejoin](/parameters/enable-mergejoin/): enable_mergejoin — Enables the planner's use of merge join plans. Observed in PG9.0–19 Beta 3; its last measured boot default is on in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [enable_nestloop](/parameters/enable-nestloop/): enable_nestloop — Enables the planner's use of nested-loop join plans. Observed in PG9.0–19 Beta 3; its last measured boot default is on in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [enable_parallel_append](/parameters/enable-parallel-append/): enable_parallel_append — Enables the planner's use of parallel append plans. Observed in PG11–19 Beta 3; its last measured boot default is on in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [enable_parallel_hash](/parameters/enable-parallel-hash/): enable_parallel_hash — Enables the planner's use of parallel hash plans. Observed in PG11–19 Beta 3; its last measured boot default is on in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [enable_partition_pruning](/parameters/enable-partition-pruning/): enable_partition_pruning — Enables plan-time and execution-time partition pruning. Observed in PG11–19 Beta 3; its last measured boot default is on in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [enable_partitionwise_aggregate](/parameters/enable-partitionwise-aggregate/): enable_partitionwise_aggregate — Enables partitionwise aggregation and grouping. Observed in PG11–19 Beta 3; its last measured boot default is off in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [enable_partitionwise_join](/parameters/enable-partitionwise-join/): enable_partitionwise_join — Enables partitionwise join. Observed in PG11–19 Beta 3; its last measured boot default is off in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [enable_presorted_aggregate](/parameters/enable-presorted-aggregate/): enable_presorted_aggregate — Enables the planner's ability to produce plans that provide presorted input for ORDER BY / DISTINCT aggregate functions. Observed in PG16–19 Beta 3; its last measured boot default is on in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [enable_self_join_elimination](/parameters/enable-self-join-elimination/): enable_self_join_elimination — Enables removal of unique self-joins. Observed in PG18–19 Beta 3; its last measured boot default is on in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [enable_seqscan](/parameters/enable-seqscan/): enable_seqscan — Enables the planner's use of sequential-scan plans. Observed in PG9.0–19 Beta 3; its last measured boot default is on in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [enable_sort](/parameters/enable-sort/): enable_sort — Enables the planner's use of explicit sort steps. Observed in PG9.0–19 Beta 3; its last measured boot default is on in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [enable_tidscan](/parameters/enable-tidscan/): enable_tidscan — Enables the planner's use of TID scan plans. Observed in PG9.0–19 Beta 3; its last measured boot default is on in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [from_collapse_limit](/parameters/from-collapse-limit/): from_collapse_limit — Sets the FROM-list size beyond which subqueries are not collapsed. Observed in PG9.0–19 Beta 3; its last measured boot default is 8 in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [geqo](/parameters/geqo/): geqo — Enables genetic query optimization. Observed in PG9.0–19 Beta 3; its last measured boot default is on in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [geqo_effort](/parameters/geqo-effort/): geqo_effort — GEQO: effort is used to set the default for other GEQO parameters. Observed in PG9.0–19 Beta 3; its last measured boot default is 5 in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [geqo_generations](/parameters/geqo-generations/): geqo_generations — GEQO: number of iterations of the algorithm. Observed in PG9.0–19 Beta 3; its last measured boot default is 0 in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [geqo_pool_size](/parameters/geqo-pool-size/): geqo_pool_size — GEQO: number of individuals in the population. Observed in PG9.0–19 Beta 3; its last measured boot default is 0 in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [geqo_seed](/parameters/geqo-seed/): geqo_seed — GEQO: seed for random path selection. Observed in PG9.0–19 Beta 3; its last measured boot default is 0 in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [geqo_selection_bias](/parameters/geqo-selection-bias/): geqo_selection_bias — GEQO: selective pressure within the population. Observed in PG9.0–19 Beta 3; its last measured boot default is 2 in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [geqo_threshold](/parameters/geqo-threshold/): geqo_threshold — Sets the threshold of FROM items beyond which GEQO is used. Observed in PG9.0–19 Beta 3; its last measured boot default is 12 in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [jit](/parameters/jit/): Allows PostgreSQL to use just-in-time compilation when the build provides a JIT implementation and the plan's estimated cost crosses the configured thresholds. Enabling it does not force JIT for every query.
- [jit_above_cost](/parameters/jit-above-cost/): jit_above_cost — Perform JIT compilation if query is more expensive. Observed in PG11–19 Beta 3; its last measured boot default is 100000 in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [jit_inline_above_cost](/parameters/jit-inline-above-cost/): jit_inline_above_cost — Perform JIT inlining if query is more expensive. Observed in PG11–19 Beta 3; its last measured boot default is 500000 in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [jit_optimize_above_cost](/parameters/jit-optimize-above-cost/): jit_optimize_above_cost — Optimize JIT-compiled functions if query is more expensive. Observed in PG11–19 Beta 3; its last measured boot default is 500000 in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [join_collapse_limit](/parameters/join-collapse-limit/): join_collapse_limit — Sets the FROM-list size beyond which JOIN constructs are not flattened. Observed in PG9.0–19 Beta 3; its last measured boot default is 8 in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [min_eager_agg_group_size](/parameters/min-eager-agg-group-size/): min_eager_agg_group_size — Sets the minimum average group size required to consider applying eager aggregation. Observed in PG19 Beta 3; its last measured boot default is 8 in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [min_parallel_index_scan_size](/parameters/min-parallel-index-scan-size/): min_parallel_index_scan_size — Sets the minimum amount of index data for a parallel scan. Observed in PG10–19 Beta 3; its last measured boot default is 512 KiB (64 × 8kB) in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [min_parallel_relation_size](/parameters/min-parallel-relation-size/): min_parallel_relation_size — Sets the minimum size of relations to be considered for parallel scan. Observed in PG9.6; its last measured boot default is 8 MiB (1024 × 8kB) in PG9.6, with user context. It was removed in PG10.
- [min_parallel_table_scan_size](/parameters/min-parallel-table-scan-size/): min_parallel_table_scan_size — Sets the minimum amount of table data for a parallel scan. Observed in PG10–19 Beta 3; its last measured boot default is 8 MiB (1024 × 8kB) in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [parallel_setup_cost](/parameters/parallel-setup-cost/): parallel_setup_cost — Sets the planner's estimate of the cost of starting up worker processes for parallel query. Observed in PG9.6–19 Beta 3; its last measured boot default is 1000 in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [parallel_tuple_cost](/parameters/parallel-tuple-cost/): parallel_tuple_cost — Sets the planner's estimate of the cost of passing each tuple (row) from worker to leader backend. Observed in PG9.6–19 Beta 3; its last measured boot default is 0.1 in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [plan_cache_mode](/parameters/plan-cache-mode/): plan_cache_mode — Controls the planner's selection of custom or generic plan. Observed in PG12–19 Beta 3; its last measured boot default is auto in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [random_page_cost](/parameters/random-page-cost/): A planner cost constant describing non-sequential page access relative to sequential access. Lowering it makes index and bitmap access paths look cheaper; it does not change storage behavior itself.
- [recursive_worktable_factor](/parameters/recursive-worktable-factor/): recursive_worktable_factor — Sets the planner's estimate of the average size of a recursive query's working table. Observed in PG15–19 Beta 3; its last measured boot default is 10 in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.
- [seq_page_cost](/parameters/seq-page-cost/): seq_page_cost — Sets the planner's estimate of the cost of a sequentially fetched disk page. Observed in PG9.0–19 Beta 3; its last measured boot default is 1 in PG19 Beta 3, with user context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.