PG14: Avoid checking output-buffer-length for every encoded byte during pg_hex_encode

Hans Buschmann <buschmann@nidsa.net>

From: Hans Buschmann <buschmann@nidsa.net>

To: "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>

Date: 2021-08-15T14:58:59Z

Lists: pgsql-hackers

Commits

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Revert refactoring of hex code to src/common/
- 1900c140554e 14.0 landed
- 2576dcfb76aa 15.0 landed
Rework refactoring of hex and encoding routines
- aef8948f38d9 14.0 cited

Attachments

hex_encode_length_check_outside_loop.patch (application/octet-stream) patch

During some development on encoding-related parts of postgres I stumbled over the new length-checking-code in common/hex.c/pg_hex_encode.

Differently when comparing it to all versions before the output-buffer-length is checked during encoding of every individual source byte.

This may impose quite a regression when using pg_dump on databases with many/big bytea or lo columns.

Because all criteria to check buffer-length are known in advance of encoding (srclen and destlen) I propose doing the check only once before starting the while-loop.

Please find the attached patch for pg14 and master, older versions did not have this behavior.

Tested on pg14-beta3, but applies also on master.

PS: This is my very first patch, I am in no way an experienced C-developer and don't have a smoothly running development environment or experience yet. (originally mostly dealing with postgres on Windows).

If it seems useful somebody could enter it as an open item / resolved item for pg14 after beta 3.

Thanks for looking!

Hans Buschmann