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| 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 | 350bd6bdc19dc53467ec2013c86fd4466c0f43af (patch) | |
| tree | 9baeea7687fa489e6c102670f27aebbd5d11ce08 /src | |
| parent | a98f01c933ec566c43d92b87a1e90467fed6217e (diff) | |
| download | postgresql-350bd6bdc19dc53467ec2013c86fd4466c0f43af.tar.gz postgresql-350bd6bdc19dc53467ec2013c86fd4466c0f43af.zip | |
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
Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/access/common/heaptuple.c | 11 | ||||
| -rw-r--r-- | src/backend/utils/adt/rangetypes.c | 3 |
2 files changed, 12 insertions, 2 deletions
diff --git a/src/backend/access/common/heaptuple.c b/src/backend/access/common/heaptuple.c index ef246c901e7..6bedbdf07ff 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 d65e5625c73..24bad529239 100644 --- a/src/backend/utils/adt/rangetypes.c +++ b/src/backend/utils/adt/rangetypes.c @@ -2608,7 +2608,8 @@ 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? */ |