diff options
| author | Bruce Momjian <bruce@momjian.us> | 2023-10-31 09:10:35 -0400 |
|---|---|---|
| committer | Bruce Momjian <bruce@momjian.us> | 2023-10-31 09:10:35 -0400 |
| commit | fbaee69bdf2a4217cd77bd6912610b4c4f01ef77 (patch) | |
| tree | 87cad5510728aec0a7c38b74f83fefd55ad16fbe | |
| parent | b3c8d1d0ea5e1a3fbde27f18ae2467b349201829 (diff) | |
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
| -rw-r--r-- | doc/src/sgml/storage.sgml | 4 | ||||
| -rw-r--r-- | src/backend/access/common/heaptuple.c | 11 | ||||
| -rw-r--r-- | src/backend/utils/adt/rangetypes.c | 3 |
3 files changed, 13 insertions, 5 deletions
diff --git a/doc/src/sgml/storage.sgml b/doc/src/sgml/storage.sgml index 002402c1ad6..bda49f6c42a 100644 --- a/doc/src/sgml/storage.sgml +++ b/doc/src/sgml/storage.sgml @@ -452,9 +452,7 @@ for storing <acronym>TOAST</acronym>-able columns on disk: <listitem> <para> <literal>PLAIN</literal> prevents either compression or - out-of-line storage; furthermore it disables use of single-byte headers - for varlena types. - This is the only possible strategy for + out-of-line storage. This is the only possible strategy for columns of non-<acronym>TOAST</acronym>-able data types. </para> </listitem> diff --git a/src/backend/access/common/heaptuple.c b/src/backend/access/common/heaptuple.c index 09b9edda456..2a71988bdc0 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 != TYPSTORAGE_PLAIN) /* Use this if it's already known varlena */ diff --git a/src/backend/utils/adt/rangetypes.c b/src/backend/utils/adt/rangetypes.c index 01ad8bc240b..f7a306669ab 100644 --- a/src/backend/utils/adt/rangetypes.c +++ b/src/backend/utils/adt/rangetypes.c @@ -2384,7 +2384,8 @@ range_contains_elem_internal(TypeCacheEntry *typcache, const RangeType *r, Datum * values into a range object. They are modeled after heaptuple.c's * heap_compute_data_size() and heap_fill_tuple(), but we need not handle * null values here. TYPE_IS_PACKABLE must test the same conditions as - * heaptuple.c's ATT_IS_PACKABLE macro. + * heaptuple.c's ATT_IS_PACKABLE macro. See the comments thare for more + * details. */ /* Does datatype allow packing into the 1-byte-header varlena format? */ |