[PATCH] Doc: document standard_conforming_strings dump/restore incompatibility

Hi,



Commit 45762084 [1] forced standard_conforming_strings to always be ON in

PostgreSQL 19. The release notes mention this change, but neither the

pg_dump/pg_restore reference pages nor the migration section note the

implications for restoring older dump files.



Dump files produced by older pg_dump versions from servers that had

standard_conforming_strings = off contain "SET standard_conforming_strings

= off" in the output. When restored into v19:



1/ Default (COPY format): pg_restore continues past the SET error and

  data restores correctly, but exits with non-zero status. With

  --exit-on-error, the restore aborts entirely.



2/ --inserts format: string literals containing backslashes may not be

  restored correctly, since the escaping conventions differ between

  standard_conforming_strings = off (source) and on (target).



The workaround is to restore into a pre-v19 server first, then produce

a fresh dump using v19 pg_dump (which forces scs=on in the source

session).



I verified this by dumping from PG18 with standard_conforming_strings =

off and restoring into PG19devel. The COPY case works because COPY has

its own escape rules independent of standard_conforming_strings. The

--inserts case results in double backslashes in the restored data.



The attached patch adds notes to:

- pg_dump reference page (Notes section)

- pg_restore reference page (Notes section)

- release-19 migration section



The patch applies cleanly on current HEAD and compiles without errors.



Discussion: https://postgr.es/m/3279216.1767072538@sss.pgh.pa.us

[1]
https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=45762084545ec14dbbe66ace1d69d7e89f8978ac

Thanks,
Baji Shaik
AWS RDS