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Support COPY TO for partitioned tables.

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Previously, COPY TO command didn't support directly specifying
partitioned tables so users had to use COPY (SELECT ...) TO variant.

This commit adds direct COPY TO support for partitioned
tables, improving both usability and performance. Performance tests
show it's faster than the COPY (SELECT ...) TO variant as it avoids
the overheads of query processing and sending results to the COPY TO
command.

When used with partitioned tables, COPY TO copies the same rows as
SELECT * FROM table. Row-level security policies of the partitioned
table are applied in the same way as when executing COPY TO on a plain
table.

Author: jian he <jian.universality@gmail.com>
Reviewed-by: vignesh C <vignesh21@gmail.com>
Reviewed-by: David Rowley <dgrowleyml@gmail.com>
Reviewed-by: Melih Mutlu <m.melihmutlu@gmail.com>
Reviewed-by: Kirill Reshke <reshkekirill@gmail.com>
Reviewed-by: Atsushi Torikoshi <torikoshia@oss.nttdata.com>
Reviewed-by: Álvaro Herrera <alvherre@kurilemu.de>
Reviewed-by: Masahiko Sawada <sawada.mshk@gmail.com>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Discussion: https://postgr.es/m/CACJufxEZt%2BG19Ors3bQUq-42-61__C%3Dy5k2wk%3DsHEFRusu7%3DiQ%40mail.gmail.com
This commit is contained in:
Masahiko Sawada
2025-10-20 10:38:52 -07:00
parent d74cfe3263
commit 4bea91f21f
9 changed files with 200 additions and 36 deletions
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11
doc/src/sgml/ref/copy.sgml
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@@ -539,13 +539,14 @@ COPY <replaceable class="parameter">count</replaceable>
<para>
<command>COPY TO</command> can be used with plain
tables and populated materialized views.
For example,
<literal>COPY <replaceable class="parameter">table</replaceable>
TO</literal> copies the same rows as
tables, populated materialized views, and partitioned tables.
For non-partitioned tables, COPY <replaceable class="parameter">table</replaceable>
copies the same rows as
<literal>SELECT * FROM ONLY <replaceable class="parameter">table</replaceable></literal>.
For partitioned tables, it copies the same rows as
<literal>SELECT * FROM <replaceable class="parameter">table</replaceable></literal>.
However it doesn't directly support other relation types,
such as partitioned tables, inheritance child tables, or views.
such as inheritance child tables, or views.
To copy all rows from such relations, use <literal>COPY (SELECT * FROM
<replaceable class="parameter">table</replaceable>) TO</literal>.
</para>