Introduce sequence_*() access functions

Similarly to tables and indexes, these functions are able to open
relations with a sequence relkind, which is useful to make a distinction
with the other relation kinds.  Previously, commands/sequence.c used a
mix of table_{close,open}() and relation_{close,open}() routines when
manipulating sequence relations, so this clarifies the code.

A direct effect of this change is to align the error messages produced
when attempting DDLs for sequences on relations with an unexpected
relkind, like a table or an index with ALTER SEQUENCE, providing an
extra error detail about the relkind of the relation used in the DDL
query.

Author: Michael Paquier
Reviewed-by: Tomas Vondra
Discussion: https://postgr.es/m/ZWlohtKAs0uVVpZ3@paquier.xyz

1 files changed, 13 insertions, 18 deletions

diff --git a/src/backend/commands/sequence.c b/src/backend/commands/sequence.c
index f7803744a5b..d019fbdede6 100644
--- a/src/backend/commands/sequence.c
+++ b/src/backend/commands/sequence.c
@@ -18,6 +18,7 @@
 #include "access/htup_details.h"
 #include "access/multixact.h"
 #include "access/relation.h"
+#include "access/sequence.h"
 #include "access/table.h"
 #include "access/transam.h"
 #include "access/xact.h"
@@ -208,7 +209,7 @@ DefineSequence(ParseState *pstate, CreateSeqStmt *seq)
 	seqoid = address.objectId;
 	Assert(seqoid != InvalidOid);
 
-	rel = table_open(seqoid, AccessExclusiveLock);
+	rel = sequence_open(seqoid, AccessExclusiveLock);
 	tupDesc = RelationGetDescr(rel);
 
 	/* now initialize the sequence's data */
@@ -219,7 +220,7 @@ DefineSequence(ParseState *pstate, CreateSeqStmt *seq)
 	if (owned_by)
 		process_owned_by(rel, owned_by, seq->for_identity);
 
-	table_close(rel, NoLock);
+	sequence_close(rel, NoLock);
 
 	/* fill in pg_sequence */
 	rel = table_open(SequenceRelationId, RowExclusiveLock);
@@ -324,7 +325,7 @@ ResetSequence(Oid seq_relid)
 	/* Note that we do not change the currval() state */
 	elm->cached = elm->last;
 
-	relation_close(seq_rel, NoLock);
+	sequence_close(seq_rel, NoLock);
 }
 
 /*
@@ -531,7 +532,7 @@ AlterSequence(ParseState *pstate, AlterSeqStmt *stmt)
 	ObjectAddressSet(address, RelationRelationId, relid);
 
 	table_close(rel, RowExclusiveLock);
-	relation_close(seqrel, NoLock);
+	sequence_close(seqrel, NoLock);
 
 	return address;
 }
@@ -555,7 +556,7 @@ SequenceChangePersistence(Oid relid, char newrelpersistence)
 	fill_seq_with_data(seqrel, &seqdatatuple);
 	UnlockReleaseBuffer(buf);
 
-	relation_close(seqrel, NoLock);
+	sequence_close(seqrel, NoLock);
 }
 
 void
@@ -662,7 +663,7 @@ nextval_internal(Oid relid, bool check_permissions)
 		Assert(elm->last_valid);
 		Assert(elm->increment != 0);
 		elm->last += elm->increment;
-		relation_close(seqrel, NoLock);
+		sequence_close(seqrel, NoLock);
 		last_used_seq = elm;
 		return elm->last;
 	}
@@ -849,7 +850,7 @@ nextval_internal(Oid relid, bool check_permissions)
 
 	UnlockReleaseBuffer(buf);
 
-	relation_close(seqrel, NoLock);
+	sequence_close(seqrel, NoLock);
 
 	return result;
 }
@@ -880,7 +881,7 @@ currval_oid(PG_FUNCTION_ARGS)
 
 	result = elm->last;
 
-	relation_close(seqrel, NoLock);
+	sequence_close(seqrel, NoLock);
 
 	PG_RETURN_INT64(result);
 }
@@ -915,7 +916,7 @@ lastval(PG_FUNCTION_ARGS)
 						RelationGetRelationName(seqrel))));
 
 	result = last_used_seq->last;
-	relation_close(seqrel, NoLock);
+	sequence_close(seqrel, NoLock);
 
 	PG_RETURN_INT64(result);
 }
@@ -1030,7 +1031,7 @@ do_setval(Oid relid, int64 next, bool iscalled)
 
 	UnlockReleaseBuffer(buf);
 
-	relation_close(seqrel, NoLock);
+	sequence_close(seqrel, NoLock);
 }
 
 /*
@@ -1095,7 +1096,7 @@ lock_and_open_sequence(SeqTable seq)
 	}
 
 	/* We now know we have the lock, and can safely open the rel */
-	return relation_open(seq->relid, NoLock);
+	return sequence_open(seq->relid, NoLock);
 }
 
 /*
@@ -1152,12 +1153,6 @@ init_sequence(Oid relid, SeqTable *p_elm, Relation *p_rel)
 	 */
 	seqrel = lock_and_open_sequence(elm);
 
-	if (seqrel->rd_rel->relkind != RELKIND_SEQUENCE)
-		ereport(ERROR,
-				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
-				 errmsg("\"%s\" is not a sequence",
-						RelationGetRelationName(seqrel))));
-
 	/*
 	 * If the sequence has been transactionally replaced since we last saw it,
 	 * discard any cached-but-unissued values.  We do not touch the currval()
@@ -1803,7 +1798,7 @@ pg_sequence_last_value(PG_FUNCTION_ARGS)
 	result = seq->last_value;
 
 	UnlockReleaseBuffer(buf);
-	relation_close(seqrel, NoLock);
+	sequence_close(seqrel, NoLock);
 
 	if (is_called)
 		PG_RETURN_INT64(result);