diff --git a/doc/src/sgml/ref/alter_property_graph.sgml b/doc/src/sgml/ref/alter_property_graph.sgml index f517f2b2d7a..d2768a4644a 100644 --- a/doc/src/sgml/ref/alter_property_graph.sgml +++ b/doc/src/sgml/ref/alter_property_graph.sgml @@ -99,7 +99,9 @@ ALTER PROPERTY GRAPH [ IF EXISTS ] nameALTER {VERTEX|NODE|EDGE|RELATIONSHIP} TABLE ... DROP LABEL - This form removes a label from an existing vertex or edge table. + This form removes a label from an existing vertex or edge table. The + last label on an element table cannot be dropped; every vertex or edge + table must have at least one label. diff --git a/src/backend/commands/propgraphcmds.c b/src/backend/commands/propgraphcmds.c index cc516e27020..aa974ca6a4f 100644 --- a/src/backend/commands/propgraphcmds.c +++ b/src/backend/commands/propgraphcmds.c @@ -1294,6 +1294,11 @@ AlterPropGraph(ParseState *pstate, const AlterPropGraphStmt *stmt) ListCell *lc; ObjectAddress pgaddress; + /* + * ShareRowExclusiveLock is required because this command runs some + * graph-wide consistency checks that wouldn't work if more than one ALTER + * PROPERTY GRAPH could operate on the same graph at once. + */ pgrelid = RangeVarGetRelidExtended(stmt->pgname, ShareRowExclusiveLock, stmt->missing_ok ? RVR_MISSING_OK : 0, @@ -1491,8 +1496,13 @@ AlterPropGraph(ParseState *pstate, const AlterPropGraphStmt *stmt) { Oid peoid; Oid labeloid; - Oid ellabeloid; + Oid ellabeloid = InvalidOid; ObjectAddress obj; + Relation ellabelrel; + SysScanDesc ellabelscan; + ScanKeyData ellabelkey[1]; + int nlabels; + HeapTuple tuple; if (stmt->element_kind == PROPGRAPH_ELEMENT_KIND_VERTEX) peoid = get_vertex_oid(pstate, pgrelid, stmt->element_alias, -1); @@ -1510,10 +1520,34 @@ AlterPropGraph(ParseState *pstate, const AlterPropGraphStmt *stmt) get_rel_name(pgrelid), stmt->element_alias, stmt->drop_label), parser_errposition(pstate, -1)); - ellabeloid = GetSysCacheOid2(PROPGRAPHELEMENTLABELELEMENTLABEL, - Anum_pg_propgraph_element_label_oid, - ObjectIdGetDatum(peoid), - ObjectIdGetDatum(labeloid)); + /* + * Is the given label associated with the element? Is this the only + * label associated with the element? Scan the + * pg_propgraph_element_label table to find answers to these + * questions. Stop scanning when we know both answers. + */ + ellabelrel = table_open(PropgraphElementLabelRelationId, AccessShareLock); + ScanKeyInit(&ellabelkey[0], + Anum_pg_propgraph_element_label_pgelelid, + BTEqualStrategyNumber, F_OIDEQ, + ObjectIdGetDatum(peoid)); + ellabelscan = systable_beginscan(ellabelrel, PropgraphElementLabelElementLabelIndexId, + true, NULL, 1, ellabelkey); + nlabels = 0; + while (HeapTupleIsValid(tuple = systable_getnext(ellabelscan))) + { + Form_pg_propgraph_element_label ellabelform = (Form_pg_propgraph_element_label) GETSTRUCT(tuple); + + nlabels++; + + if (ellabelform->pgellabelid == labeloid) + ellabeloid = ellabelform->oid; + + if (nlabels > 1 && ellabeloid) + break; + } + systable_endscan(ellabelscan); + table_close(ellabelrel, AccessShareLock); if (!ellabeloid) ereport(ERROR, @@ -1522,6 +1556,17 @@ AlterPropGraph(ParseState *pstate, const AlterPropGraphStmt *stmt) get_rel_name(pgrelid), stmt->element_alias, stmt->drop_label), parser_errposition(pstate, -1)); + /* + * Prevent dropping the last label from an element. Every element must + * have at least one label associated with it. + */ + if (nlabels == 1) + ereport(ERROR, + (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE), + errmsg("cannot drop the last label from element \"%s\"", + stmt->element_alias), + errhint("Every element must have at least one label."))); + ObjectAddressSet(obj, PropgraphElementLabelRelationId, ellabeloid); performDeletion(&obj, stmt->drop_behavior, 0); diff --git a/src/test/regress/expected/create_property_graph.out b/src/test/regress/expected/create_property_graph.out index 2f06c7ce5a8..f9960e5e0ae 100644 --- a/src/test/regress/expected/create_property_graph.out +++ b/src/test/regress/expected/create_property_graph.out @@ -57,6 +57,13 @@ ALTER PROPERTY GRAPH g3 ALTER PROPERTY GRAPH g3 ALTER VERTEX TABLE t3 DROP LABEL t3l3x; -- error ERROR: property graph "g3" element "t3" has no label "t3l3x" ALTER PROPERTY GRAPH g3 ALTER VERTEX TABLE t3 DROP LABEL t3l3; +-- Test that the last label on an element cannot be dropped +ALTER PROPERTY GRAPH g3 ALTER VERTEX TABLE t3 DROP LABEL t3l2; +ALTER PROPERTY GRAPH g3 ALTER VERTEX TABLE t3 DROP LABEL t3l1; -- error: last label +ERROR: cannot drop the last label from element "t3" +HINT: Every element must have at least one label. +-- Restore the dropped label for further tests +ALTER PROPERTY GRAPH g3 ALTER VERTEX TABLE t3 ADD LABEL t3l2 PROPERTIES ALL COLUMNS; ALTER PROPERTY GRAPH g3 DROP VERTEX TABLES (t2); -- fail ERROR: cannot drop vertex t2 of property graph g3 because other objects depend on it DETAIL: edge e1 of property graph g3 depends on vertex t2 of property graph g3 diff --git a/src/test/regress/sql/create_property_graph.sql b/src/test/regress/sql/create_property_graph.sql index 85088ae632c..b10d7191506 100644 --- a/src/test/regress/sql/create_property_graph.sql +++ b/src/test/regress/sql/create_property_graph.sql @@ -52,6 +52,11 @@ ALTER PROPERTY GRAPH g3 ADD LABEL t3l3 PROPERTIES ALL COLUMNS; ALTER PROPERTY GRAPH g3 ALTER VERTEX TABLE t3 DROP LABEL t3l3x; -- error ALTER PROPERTY GRAPH g3 ALTER VERTEX TABLE t3 DROP LABEL t3l3; +-- Test that the last label on an element cannot be dropped +ALTER PROPERTY GRAPH g3 ALTER VERTEX TABLE t3 DROP LABEL t3l2; +ALTER PROPERTY GRAPH g3 ALTER VERTEX TABLE t3 DROP LABEL t3l1; -- error: last label +-- Restore the dropped label for further tests +ALTER PROPERTY GRAPH g3 ALTER VERTEX TABLE t3 ADD LABEL t3l2 PROPERTIES ALL COLUMNS; ALTER PROPERTY GRAPH g3 DROP VERTEX TABLES (t2); -- fail ALTER PROPERTY GRAPH g3 DROP VERTEX TABLES (t2) CASCADE; ALTER PROPERTY GRAPH g3 DROP EDGE TABLES (e2);