is not using <acronym>JIT</acronym>:
<screen>
=# EXPLAIN ANALYZE SELECT SUM(relpages) FROM pg_class;
-┌─────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
-│ QUERY PLAN │
-├─────────────────────────────────────────────────────────────────────────────────────────────────────────────┤
-│ Aggregate (cost=16.27..16.29 rows=1 width=8) (actual time=0.303..0.303 rows=1 loops=1) │
-│ -> Seq Scan on pg_class (cost=0.00..15.42 rows=342 width=4) (actual time=0.017..0.111 rows=356 loops=1) │
-│ Planning Time: 0.116 ms │
-│ Execution Time: 0.365 ms │
-└─────────────────────────────────────────────────────────────────────────────────────────────────────────────┘
+ QUERY PLAN
+-------------------------------------------------------------------------------------------------------------
+ Aggregate (cost=16.27..16.29 rows=1 width=8) (actual time=0.303..0.303 rows=1 loops=1)
+ -> Seq Scan on pg_class (cost=0.00..15.42 rows=342 width=4) (actual time=0.017..0.111 rows=356 loops=1)
+ Planning Time: 0.116 ms
+ Execution Time: 0.365 ms
(4 rows)
</screen>
Given the cost of the plan, it is entirely reasonable that no
=# SET jit_above_cost = 10;
SET
=# EXPLAIN ANALYZE SELECT SUM(relpages) FROM pg_class;
-┌─────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
-│ QUERY PLAN │
-├─────────────────────────────────────────────────────────────────────────────────────────────────────────────┤
-│ Aggregate (cost=16.27..16.29 rows=1 width=8) (actual time=6.049..6.049 rows=1 loops=1) │
-│ -> Seq Scan on pg_class (cost=0.00..15.42 rows=342 width=4) (actual time=0.019..0.052 rows=356 loops=1) │
-│ Planning Time: 0.133 ms │
-│ JIT: │
-│ Functions: 3 │
-│ Generation Time: 1.259 ms │
-│ Inlining: false │
-│ Inlining Time: 0.000 ms │
-│ Optimization: false │
-│ Optimization Time: 0.797 ms │
-│ Emission Time: 5.048 ms │
-│ Execution Time: 7.416 ms │
-└─────────────────────────────────────────────────────────────────────────────────────────────────────────────┘
+ QUERY PLAN
+-------------------------------------------------------------------------------------------------------------
+ Aggregate (cost=16.27..16.29 rows=1 width=8) (actual time=6.049..6.049 rows=1 loops=1)
+ -> Seq Scan on pg_class (cost=0.00..15.42 rows=342 width=4) (actual time=0.019..0.052 rows=356 loops=1)
+ Planning Time: 0.133 ms
+ JIT:
+ Functions: 3
+ Generation Time: 1.259 ms
+ Inlining: false
+ Inlining Time: 0.000 ms
+ Optimization: false
+ Optimization Time: 0.797 ms
+ Emission Time: 5.048 ms
+ Execution Time: 7.416 ms
</screen>
As visible here, <acronym>JIT</acronym> was used, but inlining and
expensive optimization were not. If <xref