Re: About PostgreSQL Query Plan

On Mon, Jan 13, 2025 at 07:48:09PM +0300, Eşref Halıcıoğlu wrote:
> Hello,
>  
> Yes, you are right; this query is not a SELECT, it is an UPDATE query, there was a mistake in expressing it here. The columns I want
> to update here only operate on data from the last 3 months time interval.
>  
> I am also sharing the EXPLAIN ANALYZE output of the relevant query below:
>  
> Update on "TestTable1" t1  (cost=0.13..159114.84 rows=0 width=0) (actual time=0.007..0.008 rows=0 loops=1)
>   Update on "PartitionTable_2020_10" t1
… 61 lines removed …
>   Update on "PartitionTable_2025_12" t1
>   Update on "DefaultPartitionTable" t1
>   ->  Nested Loop  (cost=0.13..159114.84 rows=1 width=53) (actual time=0.006..0.006 rows=0 loops=1)
>         ->  Seq Scan on "TempTable1" tmp  (cost=0.00..19.20 rows=920 width=31) (actual time=0.006..0.006 rows=0 loops=1)
>         ->  Append  (cost=0.13..172.29 rows=64 width=38) (never executed)
>               Subplans Removed: 60
>               ->  Index Scan using partitiontable_2024_10_pkey on "PartitionTable_2024_10" t2  (cost=0.43..4.21 rows=1 width=38) (never executed)
>                     Index Cond: (("Col1" = tmp."Col2") AND ("Col3" >= (CURRENT_DATE - '3 mons'::interval)) AND ("Col3" <= CURRENT_DATE))
>                     Filter: ((NOT "IsDeleted") AND ("Col4" = tmp."Col5"))
>               ->  Index Scan using partitiontable_2024_11_pkey on "PartitionTable_2024_11" t3  (cost=0.43..4.23 rows=1 width=38) (never executed)
>                     Index Cond: (("Col1" = tmp."Col2") AND ("Col3" >= (CURRENT_DATE - '3 mons'::interval)) AND ("Col3" <= CURRENT_DATE))
>                     Filter: ((NOT "IsDeleted") AND ("Col4" = tmp."Col5"))
>               ->  Index Scan using partitiontable_2024_12_pkey on "PartitionTable_2024_12" t4  (cost=0.43..4.34 rows=1 width=38) (never executed)
>                     Index Cond: (("Col1" = tmp."Col2") AND ("Col3" >= (CURRENT_DATE - '3 mons'::interval)) AND ("Col3" <= CURRENT_DATE))
>                     Filter: ((NOT "IsDeleted") AND ("Col4" = tmp."Col5"))
>               ->  Index Scan using partitiontable_2025_01_pkey on "PartitionTable_2025_01" t5  (cost=0.43..3.72 rows=1 width=38) (never executed)
>                     Index Cond: (("Col1" = tmp."Col2") AND ("Col3" >= (CURRENT_DATE - '3 mons'::interval)) AND ("Col3" <= CURRENT_DATE))
>                     Filter: ((NOT "IsDeleted") AND ("Col4" = tmp."Col5"))
> Planning Time: 3.860 ms
> Execution Time: 0.066 ms

Well, it helped, and I missed some bits of information earlier.
Generally it looks that it was trying to scan only 4 partitions, but
they all got skipped.

Best regards,

depesz