mirror of https://github.com/postgres/postgres
Removed alter table drop column.
This commit is contained in:
Peter Eisentraut
parent
ca5771dc27
commit
306ada82c2
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@ -7,7 +7,7 @@
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*
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/commands/Attic/command.c,v 1.64 2000/01/22 14:20:45 petere Exp $
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* $Header: /cvsroot/pgsql/src/backend/commands/Attic/command.c,v 1.65 2000/01/24 23:40:35 petere Exp $
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*
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* NOTES
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* The PortalExecutorHeapMemory crap needs to be eliminated
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@ -672,209 +672,13 @@ drop_default(Oid relid, int16 attnum)
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/*
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* ALTER TABLE DROP COLUMN
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*
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* Strategy:
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* - permission/sanity checks
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* - create a new table _ATDC<name> with all attributes minus the desired one
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* - copy over all the data
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* - make the column defaults point to the new table
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* - kill the old table
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* - rename the intermediate table back
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*/
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void
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AlterTableDropColumn(const char *relationName,
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bool inh, const char *colName,
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int behavior)
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{
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Relation oldrel, newrel, defrel;
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HeapTuple tuple;
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TupleDesc olddesc, newdesc, defdsc;
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int16 dropattnum, oldnumatts;
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Oid oldrel_oid, newrel_oid;
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char tmpname[NAMEDATALEN];
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int16 i;
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HeapScanDesc scan;
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ScanKeyData scankey;
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if (!allowSystemTableMods && IsSystemRelationName(relationName))
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elog(ERROR, "ALTER TABLE: relation \"%s\" is a system catalog",
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relationName);
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#ifndef NO_SECURITY
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if (!pg_ownercheck(UserName, relationName, RELNAME))
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elog(ERROR, "ALTER TABLE: permission denied");
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#endif
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oldrel = heap_openr(relationName, AccessExclusiveLock);
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if (oldrel->rd_rel->relkind != RELKIND_RELATION)
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{
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heap_close(oldrel, AccessExclusiveLock);
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elog(ERROR, "ALTER TABLE: relation %s is not a table", relationName);
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}
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oldrel_oid = ObjectIdGetDatum(RelationGetRelid(oldrel));
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oldnumatts = RelationGetNumberOfAttributes(oldrel);
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if (oldnumatts==1)
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{
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heap_close(oldrel, AccessExclusiveLock);
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elog(ERROR, "ALTER TABLE: relation %s only has one column", relationName);
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}
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/* What to do here? */
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/*
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if (length(find_all_inheritors(RelationGetRelid(oldrel)))>0)
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elog(ERROR, "ALTER TABLE: cannot drop a column on table that is inherited from");
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*/
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/*
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* get the number of the attribute
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*/
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tuple = SearchSysCacheTuple(ATTNAME, oldrel_oid, NameGetDatum(namein(colName)), 0, 0);
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if (!HeapTupleIsValid(tuple))
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{
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heap_close(oldrel, AccessExclusiveLock);
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elog(ERROR, "ALTER TABLE: relation \"%s\" has no column \"%s\"",
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relationName, colName);
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}
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dropattnum = ((Form_pg_attribute) GETSTRUCT(tuple))->attnum;
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if (snprintf(tmpname, NAMEDATALEN, "_ATDC%s", relationName)==-1)
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{
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heap_close(oldrel, AccessExclusiveLock);
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elog(ERROR, "AlterTableDropColumn: relation name too long");
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}
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/*
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* Build descriptor for new relation
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*/
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olddesc = RelationGetDescr(oldrel);
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newdesc = CreateTemplateTupleDesc(oldnumatts-1);
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for(i = 1; i < dropattnum; i++)
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{
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Form_pg_attribute att = olddesc->attrs[i-1];
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TupleDescInitEntry(newdesc, i, nameout(&(att->attname)),
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att->atttypid, att->atttypmod,
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att->attnelems, att->attisset);
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/* the above function doesn't take care of these two */
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newdesc->attrs[i-1]->attnotnull = att->attnotnull;
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newdesc->attrs[i-1]->atthasdef = att->atthasdef;
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}
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for(i = dropattnum; i <= oldnumatts-1; i++)
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{
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Form_pg_attribute att = olddesc->attrs[i];
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TupleDescInitEntry(newdesc, i, nameout(&(att->attname)),
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att->atttypid, att->atttypmod,
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att->attnelems, att->attisset);
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/* the above function doesn't take care of these two */
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newdesc->attrs[i-1]->attnotnull = att->attnotnull;
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newdesc->attrs[i-1]->atthasdef = att->atthasdef;
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}
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/* Create the new table */
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newrel_oid = heap_create_with_catalog(tmpname, newdesc, RELKIND_RELATION, false);
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if (newrel_oid == InvalidOid)
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{
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heap_close(oldrel, AccessExclusiveLock);
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elog(ERROR, "ALTER TABLE: something went wrong");
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}
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/* Make the new table visible */
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CommandCounterIncrement();
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/*
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* Copy over the data
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*/
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newrel = heap_open(newrel_oid, AccessExclusiveLock);
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scan = heap_beginscan(oldrel, false, SnapshotNow, 0, NULL);
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while (HeapTupleIsValid(tuple = heap_getnext(scan, 0)))
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{
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bool isnull;
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Datum *new_record;
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bool *new_record_nulls;
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HeapTuple new_tuple;
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new_record = palloc((oldnumatts-1) * sizeof(*new_record));
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new_record_nulls = palloc((oldnumatts-1) * sizeof(*new_record_nulls));
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for(i = 1; i < dropattnum; i++)
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{
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new_record[i-1] = heap_getattr(tuple, i, olddesc, &isnull);
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new_record_nulls[i-1] = isnull ? 'n' : ' ';
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}
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for(i = dropattnum+1; i <= oldnumatts; i++)
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{
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new_record[i-2] = heap_getattr(tuple, i, olddesc, &isnull);
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new_record_nulls[i-2] = isnull ? 'n' : ' ';
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}
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new_tuple = heap_formtuple(newdesc, new_record, new_record_nulls);
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Assert(new_tuple);
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if (heap_insert(newrel, new_tuple) == InvalidOid)
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elog(ERROR, "AlterTableDropColumn: heap_insert failed");
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pfree(new_record);
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pfree(new_record_nulls);
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}
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heap_endscan(scan);
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heap_close(newrel, NoLock);
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heap_close(oldrel, NoLock);
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/*
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* Move defaults over to the new table
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*/
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defrel = heap_openr(AttrDefaultRelationName, AccessExclusiveLock);
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defdsc = RelationGetDescr(defrel);
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/* look for all entries referencing the old table */
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ScanKeyEntryInitialize(&scankey, 0x0, Anum_pg_attrdef_adrelid, F_OIDEQ,
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ObjectIdGetDatum(oldrel_oid));
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scan = heap_beginscan(defrel, false, SnapshotNow, 1, &scankey);
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while(HeapTupleIsValid(tuple = heap_getnext(scan, false)))
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{
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HeapTuple newtuple;
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int2 attrnum;
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Relation irelations[Num_pg_attrdef_indices];
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attrnum = ((Form_pg_attrdef) GETSTRUCT(tuple))->adnum;
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/* remove the entry about the dropped column */
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if (attrnum == dropattnum)
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{
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heap_delete(defrel, &tuple->t_self, NULL);
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continue;
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}
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newtuple = heap_copytuple(tuple);
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if (attrnum > dropattnum)
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((Form_pg_attrdef) GETSTRUCT(newtuple))->adnum--;
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/* make it point to the new table */
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((Form_pg_attrdef) GETSTRUCT(newtuple))->adrelid = newrel_oid;
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heap_update(defrel, &tuple->t_self, newtuple, NULL);
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/* keep the system catalog indices current */
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CatalogOpenIndices(Num_pg_attrdef_indices, Name_pg_attrdef_indices, irelations);
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CatalogIndexInsert(irelations, Num_pg_attrdef_indices, defrel, newtuple);
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CatalogCloseIndices(Num_pg_attrdef_indices, irelations);
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}
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heap_endscan(scan);
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heap_close(defrel, NoLock);
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CommandCounterIncrement();
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/* make the old table disappear */
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heap_drop_with_catalog(relationName);
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CommandCounterIncrement();
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/* set back original name */
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TypeRename(tmpname, relationName);
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renamerel(tmpname, relationName);
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elog(ERROR, "ALTER TABLE / DROP COLUMN is not implemented");
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}
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