From 2820adf7755d2a377546d5b55f5b1a4a39889336 Mon Sep 17 00:00:00 2001
From: Tomas Vondra
Date: Thu, 6 Apr 2023 17:18:38 +0200
Subject: Support long distance matching for zstd compression

zstd compression supports a special mode for finding matched in distant
past, which may result in better compression ratio, at the expense of
using more memory (the window size is 128MB).

To enable this optional mode, use the "long" keyword when specifying the
compression method (--compress=zstd:long).

Author: Justin Pryzby
Reviewed-by: Tomas Vondra, Jacob Champion
Discussion: https://postgr.es/m/20230224191840.GD1653@telsasoft.com
Discussion: https://postgr.es/m/20220327205020.GM28503@telsasoft.com
---
 src/backend/backup/basebackup_zstd.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

(limited to 'src/backend/backup')

diff --git a/src/backend/backup/basebackup_zstd.c b/src/backend/backup/basebackup_zstd.c
index ac6cac178a..1bb5820c88 100644
--- a/src/backend/backup/basebackup_zstd.c
+++ b/src/backend/backup/basebackup_zstd.c
@@ -118,6 +118,18 @@ bbsink_zstd_begin_backup(bbsink *sink)
 						   compress->workers, ZSTD_getErrorName(ret)));
 	}
 
+	if ((compress->options & PG_COMPRESSION_OPTION_LONG_DISTANCE) != 0)
+	{
+		ret = ZSTD_CCtx_setParameter(mysink->cctx,
+									 ZSTD_c_enableLongDistanceMatching,
+									 compress->long_distance);
+		if (ZSTD_isError(ret))
+			ereport(ERROR,
+					errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+					errmsg("could not set compression flag for %s: %s",
+						   "long", ZSTD_getErrorName(ret)));
+	}
+
 	/*
 	 * We need our own buffer, because we're going to pass different data to
 	 * the next sink than what gets passed to us.
-- 
cgit v1.2.3