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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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28
src/backend/commands/tablecmds.c
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@ -2640,8 +2640,8 @@ MergeAttributes(List *schema, List *supers, char relpersistence,
def->constraints = NIL;
def->location = -1;
if (CompressionMethodIsValid(attribute->attcompression))
def->compression = pstrdup(GetCompressionMethodName(
attribute->attcompression));
def->compression =
pstrdup(GetCompressionMethodName(attribute->attcompression));
else
def->compression = NULL;
inhSchema = lappend(inhSchema, def);
@ -6596,12 +6596,19 @@ ATExecAddColumn(List **wqueue, AlteredTableInfo *tab, Relation rel,
attribute.atttypid = typeOid;
attribute.attstattarget = (newattnum > 0) ? -1 : 0;
attribute.attlen = tform->typlen;
attribute.atttypmod = typmod;
attribute.attnum = newattnum;
attribute.attbyval = tform->typbyval;
attribute.attndims = list_length(colDef->typeName->arrayBounds);
attribute.attstorage = tform->typstorage;
attribute.atttypmod = typmod;
attribute.attbyval = tform->typbyval;
attribute.attalign = tform->typalign;
attribute.attstorage = tform->typstorage;
/* do not set compression in views etc */
if (rel->rd_rel->relkind == RELKIND_RELATION ||
rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
attribute.attcompression = GetAttributeCompression(&attribute,
colDef->compression);
else
attribute.attcompression = InvalidCompressionMethod;
attribute.attnotnull = colDef->is_not_null;
attribute.atthasdef = false;
attribute.atthasmissing = false;
@ -6612,17 +6619,6 @@ ATExecAddColumn(List **wqueue, AlteredTableInfo *tab, Relation rel,
attribute.attinhcount = colDef->inhcount;
attribute.attcollation = collOid;
/*
* lookup attribute's compression method and store it in the
* attr->attcompression.
*/
if (rel->rd_rel->relkind == RELKIND_RELATION ||
rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
attribute.attcompression = GetAttributeCompression(&attribute,
colDef->compression);
else
attribute.attcompression = InvalidCompressionMethod;
/* attribute.attacl is handled by InsertPgAttributeTuples() */
ReleaseSysCache(typeTuple);