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Re-order pg_attribute columns to eliminate some padding space.

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Now that attcompression is just a char, there's a lot of wasted
padding space after it.  Move it into the group of char-wide
columns to save a net of 4 bytes per pg_attribute entry.  While
we're at it, swap the order of attstorage and attalign to make for
a more logical grouping of these columns.

Also re-order actions in related code to match the new field ordering.

This patch also fixes one outright bug: equalTupleDescs() failed to
compare attcompression.  That could, for example, cause relcache
reload to fail to adopt a new value following a change.

Michael Paquier and Tom Lane, per a gripe from Andres Freund.

Discussion: https://postgr.es/m/20210517204803.iyk5wwvwgtjcmc5w@alap3.anarazel.de
This commit is contained in:
Tom Lane
2021-05-23 12:12:09 -04:00
parent bc2a389efb
commit f5024d8d7b
11 changed files with 80 additions and 74 deletions
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4
src/backend/access/spgist/spgutils.c
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@ -165,8 +165,8 @@ fillTypeDesc(SpGistTypeDesc *desc, Oid type)
typtup = (Form_pg_type) GETSTRUCT(tp);
desc->attlen = typtup->typlen;
desc->attbyval = typtup->typbyval;
desc->attstorage = typtup->typstorage;
desc->attalign = typtup->typalign;
desc->attstorage = typtup->typstorage;
ReleaseSysCache(tp);
}
@ -304,8 +304,8 @@ getSpGistTupleDesc(Relation index, SpGistTypeDesc *keyType)
att->attalign = keyType->attalign;
att->attstorage = keyType->attstorage;
/* We shouldn't need to bother with making these valid: */
att->attcollation = InvalidOid;
att->attcompression = InvalidCompressionMethod;
att->attcollation = InvalidOid;
/* In case we changed typlen, we'd better reset following offsets */
for (int i = spgFirstIncludeColumn; i < outTupDesc->natts; i++)
TupleDescAttr(outTupDesc, i)->attcacheoff = -1;