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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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16
src/backend/access/common/tupdesc.c
View File

@@ -424,7 +424,8 @@ equalTupleDescs(TupleDesc tupdesc1, TupleDesc tupdesc2)
* general it seems safer to check them always.
*
* attcacheoff must NOT be checked since it's possibly not set in both
* copies.
* copies. We also intentionally ignore atthasmissing, since that's
* not very relevant in tupdescs, which lack the attmissingval field.
*/
if (strcmp(NameStr(attr1->attname), NameStr(attr2->attname)) != 0)
return false;
@@ -440,9 +441,11 @@ equalTupleDescs(TupleDesc tupdesc1, TupleDesc tupdesc2)
return false;
if (attr1->attbyval != attr2->attbyval)
return false;
if (attr1->attalign != attr2->attalign)
return false;
if (attr1->attstorage != attr2->attstorage)
return false;
if (attr1->attalign != attr2->attalign)
if (attr1->attcompression != attr2->attcompression)
return false;
if (attr1->attnotnull != attr2->attnotnull)
return false;
@@ -460,7 +463,7 @@ equalTupleDescs(TupleDesc tupdesc1, TupleDesc tupdesc2)
return false;
if (attr1->attcollation != attr2->attcollation)
return false;
/* attacl, attoptions and attfdwoptions are not even present... */
/* variable-length fields are not even present... */
}
if (tupdesc1->constr != NULL)
@@ -639,12 +642,11 @@ TupleDescInitEntry(TupleDesc desc,
att->attbyval = typeForm->typbyval;
att->attalign = typeForm->typalign;
att->attstorage = typeForm->typstorage;
att->attcollation = typeForm->typcollation;
if (IsStorageCompressible(typeForm->typstorage))
att->attcompression = GetDefaultToastCompression();
else
att->attcompression = InvalidCompressionMethod;
att->attcollation = typeForm->typcollation;
ReleaseSysCache(tuple);
}
@@ -709,6 +711,7 @@ TupleDescInitBuiltinEntry(TupleDesc desc,
att->attbyval = false;
att->attalign = TYPALIGN_INT;
att->attstorage = TYPSTORAGE_EXTENDED;
att->attcompression = GetDefaultToastCompression();
att->attcollation = DEFAULT_COLLATION_OID;
break;
@@ -717,6 +720,7 @@ TupleDescInitBuiltinEntry(TupleDesc desc,
att->attbyval = true;
att->attalign = TYPALIGN_CHAR;
att->attstorage = TYPSTORAGE_PLAIN;
att->attcompression = InvalidCompressionMethod;
att->attcollation = InvalidOid;
break;
@@ -725,6 +729,7 @@ TupleDescInitBuiltinEntry(TupleDesc desc,
att->attbyval = true;
att->attalign = TYPALIGN_INT;
att->attstorage = TYPSTORAGE_PLAIN;
att->attcompression = InvalidCompressionMethod;
att->attcollation = InvalidOid;
break;
@@ -733,6 +738,7 @@ TupleDescInitBuiltinEntry(TupleDesc desc,
att->attbyval = FLOAT8PASSBYVAL;
att->attalign = TYPALIGN_DOUBLE;
att->attstorage = TYPSTORAGE_PLAIN;
att->attcompression = InvalidCompressionMethod;
att->attcollation = InvalidOid;
break;

4
src/backend/access/spgist/spgutils.c
View File

@@ -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;