Re: About PostgreSQL Query Plan

From: Eşref Halıcıoğlu <esref(dot)halicioglu(at)primeit(dot)com(dot)tr>
To: "depesz(at)depesz(dot)com" <depesz(at)depesz(dot)com>
Cc: "pgsql-general(at)lists(dot)postgresql(dot)org" <pgsql-general(at)lists(dot)postgresql(dot)org>
Subject: Re: About PostgreSQL Query Plan
Date: 2025-01-13 16:48:09
Message-ID: 260121736786553@mail.yandex.com
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<div><div><div><span style="font-size:20px;line-height:28px">Hello,</span></div><div> </div><div><div><span style="font-size:20px;line-height:28px">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.</span></div></div><div> </div><div><span style="font-size:20px;line-height:28px">I am also sharing the EXPLAIN ANALYZE output of the relevant query below:</span></div><div> </div><div><div>Update on "TestTable1" t1  (cost=0.13..159114.84 rows=0 width=0) (actual time=0.007..0.008 rows=0 loops=1)</div><div>  Update on "PartitionTable_2020_10" t1</div><div>  Update on "PartitionTable_2020_11" t1</div><div>  Update on "PartitionTable_2020_12" t1</div><div>  Update on "PartitionTable_2021_01" t1</div><div>  Update on "PartitionTable_2021_02" t1</div><div>  Update on "PartitionTable_2021_03" t1</div><div>  Update on "PartitionTable_2021_04" t1</div><div>  Update on "PartitionTable_2021_05" t1</div><div>  Update on "PartitionTable_2021_06" t1</div><div>  Update on "PartitionTable_2021_07" t1</div><div>  Update on "PartitionTable_2021_08" t1</div><div>  Update on "PartitionTable_2021_09" t1</div><div>  Update on "PartitionTable_2021_10" t1</div><div>  Update on "PartitionTable_2021_11" t1</div><div>  Update on "PartitionTable_2021_12" t1</div><div>  Update on "PartitionTable_2022_01" t1</div><div>  Update on "PartitionTable_2022_02" t1</div><div>  Update on "PartitionTable_2022_03" t1</div><div>  Update on "PartitionTable_2022_04" t1</div><div>  Update on "PartitionTable_2022_05" t1</div><div>  Update on "PartitionTable_2022_06" t1</div><div>  Update on "PartitionTable_2022_07" t1</div><div>  Update on "PartitionTable_2022_08" t1</div><div>  Update on "PartitionTable_2022_09" t1</div><div>  Update on "PartitionTable_2022_10" t1</div><div>  Update on "PartitionTable_2022_11" t1</div><div>  Update on "PartitionTable_2022_12" t1</div><div>  Update on "PartitionTable_2023_01" t1</div><div>  Update on "PartitionTable_2023_02" t1</div><div>  Update on "PartitionTable_2023_03" t1</div><div>  Update on "PartitionTable_2023_04" t1</div><div>  Update on "PartitionTable_2023_05" t1</div><div>  Update on "PartitionTable_2023_06" t1</div><div>  Update on "PartitionTable_2023_07" t1</div><div>  Update on "PartitionTable_2023_08" t1</div><div>  Update on "PartitionTable_2023_09" t1</div><div>  Update on "PartitionTable_2023_10" t1</div><div>  Update on "PartitionTable_2023_11" t1</div><div>  Update on "PartitionTable_2023_12" t1</div><div>  Update on "PartitionTable_2024_01" t1</div><div>  Update on "PartitionTable_2024_02" t1</div><div>  Update on "PartitionTable_2024_03" t1</div><div>  Update on "PartitionTable_2024_04" t1</div><div>  Update on "PartitionTable_2024_05" t1</div><div>  Update on "PartitionTable_2024_06" t1</div><div>  Update on "PartitionTable_2024_07" t1</div><div>  Update on "PartitionTable_2024_08" t1</div><div>  Update on "PartitionTable_2024_09" t1</div><div>  Update on "PartitionTable_2024_10" t2</div><div>  Update on "PartitionTable_2024_11" t3</div><div>  Update on "PartitionTable_2024_12" t4</div><div>  Update on "PartitionTable_2025_01" t5</div><div>  Update on "PartitionTable_2025_02" t1</div><div>  Update on "PartitionTable_2025_03" t1</div><div>  Update on "PartitionTable_2025_04" t1</div><div>  Update on "PartitionTable_2025_05" t1</div><div>  Update on "PartitionTable_2025_06" t1</div><div>  Update on "PartitionTable_2025_07" t1</div><div>  Update on "PartitionTable_2025_08" t1</div><div>  Update on "PartitionTable_2025_09" t1</div><div>  Update on "PartitionTable_2025_10" t1</div><div>  Update on "PartitionTable_2025_11" t1</div><div>  Update on "PartitionTable_2025_12" t1</div><div>  Update on "DefaultPartitionTable" t1</div><div>  -&gt;  Nested Loop  (cost=0.13..159114.84 rows=1 width=53) (actual time=0.006..0.006 rows=0 loops=1)</div><div>        -&gt;  Seq Scan on "TempTable1" tmp  (cost=0.00..19.20 rows=920 width=31) (actual time=0.006..0.006 rows=0 loops=1)</div><div>        -&gt;  Append  (cost=0.13..172.29 rows=64 width=38) (never executed)</div><div>              Subplans Removed: 60</div><div>              -&gt;  Index Scan using partitiontable_2024_10_pkey on "PartitionTable_2024_10" t2  (cost=0.43..4.21 rows=1 width=38) (never executed)</div><div>                    Index Cond: (("Col1" = tmp."Col2") AND ("Col3" &gt;= (CURRENT_DATE - '3 mons'::interval)) AND ("Col3" &lt;= CURRENT_DATE))</div><div>                    Filter: ((NOT "IsDeleted") AND ("Col4" = tmp."Col5"))</div><div>              -&gt;  Index Scan using partitiontable_2024_11_pkey on "PartitionTable_2024_11" t3  (cost=0.43..4.23 rows=1 width=38) (never executed)</div><div>                    Index Cond: (("Col1" = tmp."Col2") AND ("Col3" &gt;= (CURRENT_DATE - '3 mons'::interval)) AND ("Col3" &lt;= CURRENT_DATE))</div><div>                    Filter: ((NOT "IsDeleted") AND ("Col4" = tmp."Col5"))</div><div>              -&gt;  Index Scan using partitiontable_2024_12_pkey on "PartitionTable_2024_12" t4  (cost=0.43..4.34 rows=1 width=38) (never executed)</div><div>                    Index Cond: (("Col1" = tmp."Col2") AND ("Col3" &gt;= (CURRENT_DATE - '3 mons'::interval)) AND ("Col3" &lt;= CURRENT_DATE))</div><div>                    Filter: ((NOT "IsDeleted") AND ("Col4" = tmp."Col5"))</div><div>              -&gt;  Index Scan using partitiontable_2025_01_pkey on "PartitionTable_2025_01" t5  (cost=0.43..3.72 rows=1 width=38) (never executed)</div><div>                    Index Cond: (("Col1" = tmp."Col2") AND ("Col3" &gt;= (CURRENT_DATE - '3 mons'::interval)) AND ("Col3" &lt;= CURRENT_DATE))</div><div>                    Filter: ((NOT "IsDeleted") AND ("Col4" = tmp."Col5"))</div><div>Planning Time: 3.860 ms</div><div>Execution Time: 0.066 ms</div></div><div> </div><div><span style="font-size:20px;line-height:28px">Thank you for your interest and support.</span></div><div> </div><div><span style="font-size:20px;line-height:28px">Good work,</span></div><div> </div><div><span style="font-size:20px;line-height:28px">Eşref Halıcıoğlu</span></div></div><div> </div><div> </div><div> </div></div><div> </div><div>----------------</div><div>To: Eşref Halıcıoğlu (esref(dot)halicioglu(at)primeit(dot)com(dot)tr);</div><div>Cc: pgsql-general(at)lists(dot)postgresql(dot)org;</div><div>Subject: About PostgreSQL Query Plan;</div><div>13.01.2025, 18:42, "hubert depesz lubaczewski" &lt;depesz(at)depesz(dot)com&gt;:</div><blockquote><p>On Mon, Jan 13, 2025 at 05:26:09PM +0300, Eşref Halıcıoğlu wrote:</p><blockquote> Hello,<br />  <br /> I have a query in PostgreSQL and I want this query to retrieve only data from the last 3 months. However, when I examine the query<br /> plan, I see that all partitions are listed.</blockquote><p><br />Please note that your explain is for update, not select (which<br />"retrieve" in your mail would suggest).<br /> </p><blockquote> This raises a few questions in my mind:<br /> <br />   • Are all partitions really being accessed, or only the partitions of the last 3 months are being accessed while the other<br />     partitions have to be shown in the query plan?</blockquote><p><br />Not really possible to tell without reading explain *analyze*.<br />Potentially all. But perhaps just fewer.<br /><br />Best regards,<br /><br />depesz<br /> </p></blockquote><div> </div><div> </div><div>-- </div><div><img src="https://avatars.mds.yandex.net/get-mail-signature/1640102/65bb545ae0f44457010ad3aaa33d1fca/orig" /></div><div> </div>

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