Add vacuum_truncate configuration parameter.

This new parameter works just like the storage parameter of the
same name: if set to true (which is the default), autovacuum and
VACUUM attempt to truncate any empty pages at the end of the table.
It is primarily intended to help users avoid locking issues on hot
standbys.  The setting can be overridden with the storage parameter
or VACUUM's TRUNCATE option.

Since there's presently no way to determine whether a Boolean
storage parameter is explicitly set or has just picked up the
default value, this commit also introduces an isset_offset member
to relopt_parse_elt.

Suggested-by: Will Storey <[email protected]>
Author: Nathan Bossart <[email protected]>
Co-authored-by: Gurjeet Singh <[email protected]>
Reviewed-by: Laurenz Albe <[email protected]>
Reviewed-by: Fujii Masao <[email protected]>
Reviewed-by: Robert Treat <[email protected]>
Discussion: https://postgr.es/m/Z2DE4lDX4tHqNGZt%40dev.null

1 files changed, 1 insertions, 0 deletions

diff --git a/src/include/access/reloptions.h b/src/include/access/reloptions.h
index 43445cdcc6c..146aed47c2d 100644
--- a/src/include/access/reloptions.h
+++ b/src/include/access/reloptions.h
@@ -152,6 +152,7 @@ typedef struct
 	const char *optname;		/* option's name */
 	relopt_type opttype;		/* option's datatype */
 	int			offset;			/* offset of field in result struct */
+	int			isset_offset;	/* if > 0, offset of "is set" field */
 } relopt_parse_elt;
 
 /* Local reloption definition */