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Use valid compression method in brin_form_tuple

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When compressing the BRIN summary, we can't simply use the compression
method from the indexed attribute.  The summary may use a different data
type, e.g. fixed-length attribute may have varlena summary, leading to
compression failures.  For the built-in BRIN opclasses this happens to
work, because the summary uses the same data type as the attribute.

When the data types match, we can inherit use the compression method
specified for the attribute (it's copied into the index descriptor).
Otherwise we don't have much choice and have to use the default one.

Author: Tomas Vondra
Reviewed-by: Justin Pryzby <pryzby@telsasoft.com>
Discussion: https://postgr.es/m/e0367f27-392c-321a-7411-a58e1a7e4817%40enterprisedb.com
This commit is contained in:
Tomas Vondra 2021-03-21 00:28:13 +01:00
parent aa25d1089a
commit 882b2cdc08
1 changed files with 14 additions and 2 deletions
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16
src/backend/access/brin/brin_tuple.c
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@ -213,10 +213,22 @@ brin_form_tuple(BrinDesc *brdesc, BlockNumber blkno, BrinMemTuple *tuple,
(atttype->typstorage == TYPSTORAGE_EXTENDED ||
atttype->typstorage == TYPSTORAGE_MAIN))
{
Datum cvalue;
char compression;
Form_pg_attribute att = TupleDescAttr(brdesc->bd_tupdesc,
keyno);
Datum cvalue = toast_compress_datum(value,
att->attcompression);
/*
* If the BRIN summary and indexed attribute use the same data
* type, we can use the same compression method. Otherwise we
* have to use the default method.
*/
if (att->atttypid == atttype->type_id)
compression = att->attcompression;
else
compression = GetDefaultToastCompression();
cvalue = toast_compress_datum(value, compression);
if (DatumGetPointer(cvalue) != NULL)
{