<xref linkend="sql-explain"/> can be used to see whether

<acronym>JIT</acronym> is used or not. As an example, here is a query that

is not using <acronym>JIT</acronym>:

=# EXPLAIN ANALYZE SELECT SUM(relpages) FROM pg_class;

┌─────────────────────────────────────────────────────────────────────────────────────────────────────────────┐

│ QUERY PLAN │

│ Execution Time: 0.365 ms │

└─────────────────────────────────────────────────────────────────────────────────────────────────────────────┘

(4 rows)

Given the cost of the plan, it is entirely reasonable that no

<acronym>JIT</acronym> was used, the cost of <acronym>JIT</acronym> would

have been bigger than the savings. Adjusting the cost limits will lead to

<acronym>JIT</acronym> use:

=# SET jit_above_cost = 10;

SET

=# EXPLAIN ANALYZE SELECT SUM(relpages) FROM pg_class;

│ Emission Time: 5.048 ms │

│ Execution Time: 7.416 ms │

└─────────────────────────────────────────────────────────────────────────────────────────────────────────────┘

As visible here, <acronym>JIT</acronym> was used, but inlining and

expensive optimization were not. If <xref

linkend="guc-jit-optimize-above-cost"/>, <xref

<function>_PG_jit_provider_init</function>. This function is passed a

struct that needs to be filled with the callback function pointers for

individual actions.

struct JitProviderCallbacks

{

JitProviderResetAfterErrorCB reset_after_error;

JitProviderReleaseContextCB release_context;

JitProviderCompileExprCB compile_expr;

};

extern void _PG_jit_provider_init(JitProviderCallbacks *cb);

</para>

</sect3>

</sect2>

</para>

<para>

Examples:

websearch_to_tsquery

websearch_to_tsquery

</para>

</sect2>