From 7d559c8580f722dc40f2c34573e53e33626679e0 Mon Sep 17 00:00:00 2001 From: Nathan Bossart Date: Mon, 24 Mar 2025 15:47:02 -0500 Subject: Expand comment for isset_offset. This field was added in commit 0164a0f9ee to provide a way to determine whether a storage parameter was explicitly set for the relation or if it just picked up the default value. In most cases, this can be accomplished by giving the storage parameter a special out-of-range default value (e.g., the autovacuum_vacuum_insert_threshold storage parameter defaults to -2), but this approach doesn't work in all cases. For example, a Boolean storage parameter cannot be given an out-of-range default, so we need another way to discover the source of its value. Reported-by: "David G. Johnston" Reviewed-by: "David G. Johnston" Discussion: https://postgr.es/m/CAKFQuwYKtEUYKS%2B18gRs-xPhn0qOJgM2KGyyWVCODHuVn9F-XQ%40mail.gmail.com --- src/include/access/reloptions.h | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) (limited to 'src') diff --git a/src/include/access/reloptions.h b/src/include/access/reloptions.h index 146aed47c2d..dfbb4c85460 100644 --- a/src/include/access/reloptions.h +++ b/src/include/access/reloptions.h @@ -152,7 +152,19 @@ 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 */ + + /* + * isset_offset is an optional offset of a field in the result struct that + * stores whether the option is explicitly set for the relation or if it + * just picked up the default value. In most cases, this can be + * accomplished by giving the reloption a special out-of-range default + * value (e.g., some integer reloptions use -2), but this isn't always + * possible. For example, a Boolean reloption cannot be given an + * out-of-range default, so we need another way to discover the source of + * its value. This offset is only used if given a value greater than + * zero. + */ + int isset_offset; } relopt_parse_elt; /* Local reloption definition */ -- cgit v1.2.3