From 4e10f552e88087650bec97ee141b8dd70e74d405 Mon Sep 17 00:00:00 2001 From: Jelte Fennema-Nio Date: Fri, 30 Jan 2026 11:58:50 +0100 Subject: [PATCH v1] Change default of jit to off While jit can speed up slow analytical queries, it can also cause huge slowdowns on otherwise very fast queries. This can be especially painful when due to some unrelated changes (e.g. a few additional INSERTs into a talbe) the plan is changed to use jit and then results in a huge performance cliff. That's why the default is already off on all hyperscalers. This changes our default to align with that that. --- doc/src/sgml/config.sgml | 3 ++- src/backend/jit/jit.c | 2 +- src/backend/utils/misc/guc_parameters.dat | 2 +- src/backend/utils/misc/postgresql.conf.sample | 2 +- 4 files changed, 5 insertions(+), 4 deletions(-) diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml index 5560b95ee60..e78ad2d3e25 100644 --- a/doc/src/sgml/config.sgml +++ b/doc/src/sgml/config.sgml @@ -6510,7 +6510,8 @@ SELECT * FROM parent WHERE key = 2400; Determines whether JIT compilation may be used by PostgreSQL, if available (see ). - The default is on. + The default is off (before + PostgreSQL 19 the default was on). diff --git a/src/backend/jit/jit.c b/src/backend/jit/jit.c index e92be36932b..1c6261096d0 100644 --- a/src/backend/jit/jit.c +++ b/src/backend/jit/jit.c @@ -29,7 +29,7 @@ #include "utils/fmgrprotos.h" /* GUCs */ -bool jit_enabled = true; +bool jit_enabled = false; char *jit_provider = NULL; bool jit_debugging_support = false; bool jit_dump_bitcode = false; diff --git a/src/backend/utils/misc/guc_parameters.dat b/src/backend/utils/misc/guc_parameters.dat index f0260e6e412..a164d92d439 100644 --- a/src/backend/utils/misc/guc_parameters.dat +++ b/src/backend/utils/misc/guc_parameters.dat @@ -1356,7 +1356,7 @@ short_desc => 'Allow JIT compilation.', flags => 'GUC_EXPLAIN', variable => 'jit_enabled', - boot_val => 'true', + boot_val => 'false', }, { name => 'jit_above_cost', type => 'real', context => 'PGC_USERSET', group => 'QUERY_TUNING_COST', diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample index c4f92fcdac8..a277cf560ea 100644 --- a/src/backend/utils/misc/postgresql.conf.sample +++ b/src/backend/utils/misc/postgresql.conf.sample @@ -469,7 +469,7 @@ #constraint_exclusion = partition # on, off, or partition #cursor_tuple_fraction = 0.1 # range 0.0-1.0 #from_collapse_limit = 8 -#jit = on # allow JIT compilation +#jit = off # allow JIT compilation #join_collapse_limit = 8 # 1 disables collapsing of explicit # JOIN clauses #plan_cache_mode = auto # auto, force_generic_plan or base-commit: 1eb09ed63a8d8063dc6bb75c8f31ec564bf35250 -- 2.52.0