From adb82235b54c4746d0ca75a6d9c5b02aef7310fa Mon Sep 17 00:00:00 2001 From: Bruce Momjian Date: Tue, 31 Oct 2023 09:10:35 -0400 Subject: doc: 1-byte varlena headers can be used for user PLAIN storage This also updates some C comments. Reported-by: suchithjn22@gmail.com Discussion: https://postgr.es/m/167336599095.2667301.15497893107226841625@wrigleys.postgresql.org Author: Laurenz Albe (doc patch) Backpatch-through: 11 --- src/backend/access/common/heaptuple.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) (limited to 'src/backend/access/common/heaptuple.c') diff --git a/src/backend/access/common/heaptuple.c b/src/backend/access/common/heaptuple.c index ada089a3362..da7beca8227 100644 --- a/src/backend/access/common/heaptuple.c +++ b/src/backend/access/common/heaptuple.c @@ -68,7 +68,16 @@ #include "utils/memutils.h" -/* Does att's datatype allow packing into the 1-byte-header varlena format? */ +/* + * Does att's datatype allow packing into the 1-byte-header varlena format? + * While functions that use TupleDescAttr() and assign attstorage = + * TYPSTORAGE_PLAIN cannot use packed varlena headers, functions that call + * TupleDescInitEntry() use typeForm->typstorage (TYPSTORAGE_EXTENDED) and + * can use packed varlena headers, e.g.: + * CREATE TABLE test(a VARCHAR(10000) STORAGE PLAIN); + * INSERT INTO test VALUES (repeat('A',10)); + * This can be verified with pageinspect. + */ #define ATT_IS_PACKABLE(att) \ ((att)->attlen == -1 && (att)->attstorage != 'p') /* Use this if it's already known varlena */ -- cgit v1.2.3