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Help with an interesting Postgres question: Why isn't an Index Only Scan used on a partition accessed via the parent table?.
version |
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PostgreSQL 12.9 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 8.5.0 20210514 (Red Hat 8.5.0-4), 64-bit |
1 rows affected
QUERY PLAN |
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ProjectSet (cost=251.78..5251.81 rows=1000000 width=36) (actual rows=1000000 loops=1) |
InitPlan 1 (returns $0) |
-> Seq Scan on test (cost=0.00..22.70 rows=1270 width=32) (actual rows=1 loops=1) |
-> Aggregate (cost=229.08..229.09 rows=1 width=32) (actual rows=1 loops=1) |
-> Nested Loop (cost=0.01..219.56 rows=3810 width=40) (actual rows=4 loops=1) |
-> Seq Scan on test t (cost=0.00..22.70 rows=1270 width=32) (actual rows=1 loops=1) |
-> Function Scan on unnest x (cost=0.01..0.13 rows=3 width=40) (actual rows=4 loops=1) |
Filter: (num > 1) |
Rows Removed by Filter: 1 |
Planning Time: 0.567 ms |
Execution Time: 1032.430 ms |
QUERY PLAN |
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ProjectSet (cost=0.00..6350041.75 rows=1270000000 width=36) (actual rows=1000000 loops=1) |
-> Seq Scan on test (cost=0.00..22.70 rows=1270 width=32) (actual rows=1 loops=1) |
Planning Time: 0.063 ms |
Execution Time: 1148.343 ms |
QUERY PLAN |
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ProjectSet (cost=0.00..6350079.85 rows=1270000000 width=36) (actual rows=1000000 loops=1) |
-> Seq Scan on test (cost=0.00..22.70 rows=1270 width=32) (actual rows=1 loops=1) |
Planning Time: 0.093 ms |
Execution Time: 1587.569 ms |
QUERY PLAN |
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ProjectSet (cost=0.00..6350070.33 rows=1270000000 width=36) (actual rows=1000000 loops=1) |
-> Seq Scan on test (cost=0.00..22.70 rows=1270 width=32) (actual rows=1 loops=1) |
Planning Time: 0.071 ms |
Execution Time: 1859.762 ms |
QUERY PLAN |
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ProjectSet (cost=0.00..6350035.40 rows=1270000000 width=36) (actual rows=1000000 loops=1) |
-> Seq Scan on test (cost=0.00..22.70 rows=1270 width=32) (actual rows=1 loops=1) |
Planning Time: 0.064 ms |
Execution Time: 2622.909 ms |
QUERY PLAN |
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ProjectSet (cost=0.00..6350051.28 rows=1270000000 width=36) (actual rows=1000000 loops=1) |
-> Seq Scan on test (cost=0.00..22.70 rows=1270 width=32) (actual rows=1 loops=1) |
Planning Time: 0.067 ms |
Execution Time: 711.168 ms |