char *compression;

chartypstorage;

Oidcmoid;

Datumvalues[Natts_pg_attribute];

boolnulls[Natts_pg_attribute];

boolreplace[Natts_pg_attribute];

ObjectAddress address;

Assert(IsA(newValue, String));

compression = strVal(newValue);

attrel = table_open(AttributeRelationId, RowExclusiveLock);

tuple = SearchSysCacheAttName(RelationGetRelid(rel), column);

/* copy the cache entry so we can scribble on it below */

tuple = SearchSysCacheCopyAttName(RelationGetRelid(rel), column);

if (!HeapTupleIsValid(tuple))

ereport(ERROR,

(errcode(ERRCODE_UNDEFINED_COLUMN),

errmsg("column data type %s does not support compression",

format_type_be(atttableform->atttypid))));

/* initialize buffers for new tuple values */

memset(values, 0, sizeof(values));

memset(nulls, false, sizeof(nulls));

memset(replace, false, sizeof(replace));

/* get the attribute compression method. */

cmoid = GetAttributeCompression(atttableform, compression);

/* update pg_attribute entry */

atttableform->attcompression = cmoid;

CatalogTupleUpdate(attrel, &tuple->t_self, tuple);

InvokeObjectPostAlterHook(RelationRelationId,

RelationGetRelid(rel),

atttableform->attnum);

ReleaseSysCache(tuple);

attnum);

/* apply changes to the index column as well */

/*

* Apply the change to indexes as well (only for simple index columns,

* matching behavior of index.c ConstructTupleDescriptor()).

*/

SetIndexStorageProperties(rel, attrel, attnum, cmoid, '\0', lockmode);

heap_freetuple(tuple);

table_close(attrel, RowExclusiveLock);

/* make changes visible */

CommandCounterIncrement();

ObjectAddressSubSet(address, RelationRelationId,

RelationGetRelid(rel),atttableform->attnum);

RelationGetRelid(rel), attnum);

return address;

}