apache · jrgemignani · Oct 12, 2023 · Oct 11, 2023
diff --git a/regress/expected/cypher_delete.out b/regress/expected/cypher_delete.out
@@ -62,9 +62,9 @@ SELECT * FROM cypher('cypher_delete', $$CREATE (:v)-[:e]->(:v)$$) AS (a agtype);
 
 --Should Fail
 SELECT * FROM cypher('cypher_delete', $$MATCH(n1)-[e]->(n2) DELETE n1 RETURN n1$$) AS (a agtype);
-ERROR:  Cannot delete vertex n1, because it still has edges attached. To delete this vertex, you must first delete the attached edges.
+ERROR:  Cannot delete a vertex that has edge(s). Delete the edge(s) first, or try DETACH DELETE.
 SELECT * FROM cypher('cypher_delete', $$MATCH(n1)-[e]->(n2) DELETE n2 RETURN n2$$) AS (a agtype);
-ERROR:  Cannot delete vertex n2, because it still has edges attached. To delete this vertex, you must first delete the attached edges.
+ERROR:  Cannot delete a vertex that has edge(s). Delete the edge(s) first, or try DETACH DELETE.
 SELECT * FROM cypher('cypher_delete', $$MATCH(n1)-[e]->(n2) DELETE e RETURN e$$) AS (a agtype);
                                                            a                                                            
 ------------------------------------------------------------------------------------------------------------------------
@@ -188,7 +188,7 @@ SELECT * FROM cypher('cypher_delete', $$CREATE (n:v)-[:e]->(:v) CREATE (n)-[:e]-
 (0 rows)
 
 SELECT * FROM cypher('cypher_delete', $$MATCH(n1)-[]->() DELETE n1 RETURN n1$$) AS (a agtype);
-ERROR:  Cannot delete vertex n1, because it still has edges attached. To delete this vertex, you must first delete the attached edges.
+ERROR:  Cannot delete a vertex that has edge(s). Delete the edge(s) first, or try DETACH DELETE.
 --Cleanup
 SELECT * FROM cypher('cypher_delete', $$MATCH(n) DETACH DELETE n RETURN n$$) AS (a agtype);
                                 a                                
@@ -234,7 +234,7 @@ SELECT * FROM cypher('cypher_delete', $$CREATE (n:v)-[:e]->(:v)$$) AS (a agtype)
 (0 rows)
 
 SELECT * FROM cypher('cypher_delete', $$MATCH(n1)-[e]->() DELETE n1, e RETURN n1$$) AS (a agtype);
-ERROR:  Cannot delete vertex n1, because it still has edges attached. To delete this vertex, you must first delete the attached edges.
+ERROR:  Cannot delete a vertex that has edge(s). Delete the edge(s) first, or try DETACH DELETE.
 --Cleanup
 SELECT * FROM cypher('cypher_delete', $$MATCH(n) DETACH DELETE n RETURN n$$) AS (a agtype);
                                 a                                
@@ -651,6 +651,113 @@ SELECT * FROM cypher('cypher_delete', $$MATCH (u:vertices) RETURN u $$) AS (resu
 --------
 (0 rows)
 
+--
+-- Detach Delete
+--
+SELECT create_graph('detach_delete');
+NOTICE:  graph "detach_delete" has been created
+ create_graph 
+--------------
+
+(1 row)
+
+SELECT * FROM cypher('detach_delete',
+$$
+    CREATE (x:Label3{name:'x', delete: true}),
+           (y:Label3{name:'y', delete: true}),
+           (a:Label1{name:'a', delete: true}),
+           (b:Label5{name:'b'}),
+           (c:Label5{name:'c'}),
+           (d:Label5{name:'d'}),
+           (m:Label7{name:'m', delete: true}),
+           (n:Label2{name:'n'}),
+           (p:Label2{name:'p'}),
+           (q:Label2{name:'q'}),
+           (a)-[:rel1{name:'ab'}]->(b),
+           (c)-[:rel2{name:'cd'}]->(d),
+           (n)-[:rel3{name:'nm'}]->(m),
+           (a)-[:rel4{name:'am'}]->(m),
+           (p)-[:rel5{name:'pq'}]->(q)
+$$
+) as (a agtype);
+ a 
+---
+(0 rows)
+
+-- no vertices or edges are deleted (error is expected)
+SELECT * FROM cypher('detach_delete', $$ MATCH (x:Label1), (y:Label3), (z:Label7) DELETE x, y, z RETURN 1 $$) as (a agtype);
+ERROR:  Cannot delete a vertex that has edge(s). Delete the edge(s) first, or try DETACH DELETE.
+SELECT * FROM cypher('detach_delete', $$ MATCH (v) RETURN v.name $$) as (vname agtype);
+ vname 
+-------
+ "x"
+ "y"
+ "a"
+ "b"
+ "c"
+ "d"
+ "m"
+ "n"
+ "p"
+ "q"
+(10 rows)
+
+SELECT * FROM cypher('detach_delete', $$ MATCH ()-[e]->() RETURN e.name $$) as (ename agtype);
+ ename 
+-------
+ "ab"
+ "cd"
+ "nm"
+ "am"
+ "pq"
+(5 rows)
+
+-- x, y, a, m, ab, nm, am are deleted
+SELECT * FROM cypher('detach_delete', $$ MATCH (x:Label1), (y:Label3), (z:Label7) DETACH DELETE x, y, z RETURN 1 $$) as (a agtype);
+ a 
+---
+ 1
+ 1
+(2 rows)
+
+SELECT * FROM cypher('detach_delete', $$ MATCH (v) RETURN v.name $$) as (vname agtype);
+ vname 
+-------
+ "b"
+ "c"
+ "d"
+ "n"
+ "p"
+ "q"
+(6 rows)
+
+SELECT * FROM cypher('detach_delete', $$ MATCH ()-[e]->() RETURN e.name $$) as (ename agtype);
+ ename 
+-------
+ "cd"
+ "pq"
+(2 rows)
+
+SELECT drop_graph('detach_delete', true);
+NOTICE:  drop cascades to 12 other objects
+DETAIL:  drop cascades to table detach_delete._ag_label_vertex
+drop cascades to table detach_delete._ag_label_edge
+drop cascades to table detach_delete."Label3"
+drop cascades to table detach_delete."Label1"
+drop cascades to table detach_delete."Label5"
+drop cascades to table detach_delete."Label7"
+drop cascades to table detach_delete."Label2"
+drop cascades to table detach_delete.rel1
+drop cascades to table detach_delete.rel2
+drop cascades to table detach_delete.rel3
+drop cascades to table detach_delete.rel4
+drop cascades to table detach_delete.rel5
+NOTICE:  graph "detach_delete" has been dropped
+ drop_graph 
+------------
+
+(1 row)
+
 --
 -- Clean up
 --

diff --git a/regress/sql/cypher_delete.sql b/regress/sql/cypher_delete.sql
@@ -246,6 +246,43 @@ END;
 
 SELECT * FROM cypher('cypher_delete', $$MATCH (u:vertices) RETURN u $$) AS (result agtype);
 
+--
+-- Detach Delete
+--
+
+SELECT create_graph('detach_delete');
+SELECT * FROM cypher('detach_delete',
+$$
+    CREATE (x:Label3{name:'x', delete: true}),
+           (y:Label3{name:'y', delete: true}),
+           (a:Label1{name:'a', delete: true}),
+           (b:Label5{name:'b'}),
+           (c:Label5{name:'c'}),
+           (d:Label5{name:'d'}),
+           (m:Label7{name:'m', delete: true}),
+           (n:Label2{name:'n'}),
+           (p:Label2{name:'p'}),
+           (q:Label2{name:'q'}),
+           (a)-[:rel1{name:'ab'}]->(b),
+           (c)-[:rel2{name:'cd'}]->(d),
+           (n)-[:rel3{name:'nm'}]->(m),
+           (a)-[:rel4{name:'am'}]->(m),
+           (p)-[:rel5{name:'pq'}]->(q)
+$$
+) as (a agtype);
+
+-- no vertices or edges are deleted (error is expected)
+SELECT * FROM cypher('detach_delete', $$ MATCH (x:Label1), (y:Label3), (z:Label7) DELETE x, y, z RETURN 1 $$) as (a agtype);
+SELECT * FROM cypher('detach_delete', $$ MATCH (v) RETURN v.name $$) as (vname agtype);
+SELECT * FROM cypher('detach_delete', $$ MATCH ()-[e]->() RETURN e.name $$) as (ename agtype);
+
+-- x, y, a, m, ab, nm, am are deleted
+SELECT * FROM cypher('detach_delete', $$ MATCH (x:Label1), (y:Label3), (z:Label7) DETACH DELETE x, y, z RETURN 1 $$) as (a agtype);
+SELECT * FROM cypher('detach_delete', $$ MATCH (v) RETURN v.name $$) as (vname agtype);
+SELECT * FROM cypher('detach_delete', $$ MATCH ()-[e]->() RETURN e.name $$) as (ename agtype);
+
+SELECT drop_graph('detach_delete', true);
+
 --
 -- Clean up
 --

diff --git a/src/backend/executor/cypher_delete.c b/src/backend/executor/cypher_delete.c
@@ -32,6 +32,7 @@
 #include "parser/parsetree.h"
 #include "storage/bufmgr.h"
 #include "utils/rel.h"
+#include "common/hashfn.h"
 
 #include "catalog/ag_label.h"
 #include "executor/cypher_executor.h"
@@ -48,9 +49,7 @@ static void rescan_cypher_delete(CustomScanState *node);
 
 static void process_delete_list(CustomScanState *node);
 
-static void find_connected_edges(CustomScanState *node, char *graph_name,
-                                 List *labels, char *var_name, graphid id,
-                                 bool detach_delete);
+static void check_for_connected_edges(CustomScanState *node);
 static agtype_value *extract_entity(CustomScanState *node,
                                     TupleTableSlot *scanTupleSlot,
                                     int entity_position);
@@ -83,6 +82,7 @@ static void begin_cypher_delete(CustomScanState *node, EState *estate,
     cypher_delete_custom_scan_state *css =
         (cypher_delete_custom_scan_state *)node;
     Plan *subplan;
+    HASHCTL hashctl;
 
     Assert(list_length(css->cs->custom_plans) == 1);
 
@@ -112,6 +112,16 @@ static void begin_cypher_delete(CustomScanState *node, EState *estate,
      */
     css->edge_labels = get_all_edge_labels_per_graph(estate, css->delete_data->graph_oid);
 
+    /* init vertex_id_htab */
+    MemSet(&hashctl, 0, sizeof(hashctl));
+    hashctl.keysize = sizeof(graphid);
+    hashctl.entrysize =
+        sizeof(graphid); // entries are not used, but entrysize must >= keysize
+    hashctl.hash = tag_hash;
+    css->vertex_id_htab = hash_create(DELETE_VERTEX_HTAB_NAME,
+                                      DELETE_VERTEX_HTAB_SIZE, &hashctl,
+                                      HASH_ELEM | HASH_FUNCTION);
+
     /*
      * Postgres does not assign the es_output_cid in queries that do
      * not write to disk, ie: SELECT commands. We need the command id
@@ -194,6 +204,10 @@ static TupleTableSlot *exec_cypher_delete(CustomScanState *node)
  */
 static void end_cypher_delete(CustomScanState *node)
 {
+    check_for_connected_edges(node);
+
+    hash_destroy(((cypher_delete_custom_scan_state *)node)->vertex_id_htab);
+
     ExecEndNode(node->ss.ps.lefttree);
 }
 
@@ -443,15 +457,15 @@ static void process_delete_list(CustomScanState *node)
         }
 
         /*
-         * For vertices, we need to check if the vertex is connected to any
-         * edges, * if there are, we need to delete them or throw an error,
-         * depending on if the query specified the DETACH option.
+         * For vertices, we insert the vertex ID in the hashtable
+         * vertex_id_htab. This hashtable is used later to process
+         * connected edges.
          */
         if (original_entity_value->type == AGTV_VERTEX)
         {
-            find_connected_edges(node, css->delete_data->graph_name,
-                                 css->edge_labels, item->var_name,
-                                 id->val.int_value, css->delete_data->detach);
+            bool found;
+            hash_search(css->vertex_id_htab, (void *)&(id->val.int_value),
+                        HASH_ENTER, &found);
         }
 
         /* At this point, we are ready to delete the node/vertex. */
@@ -464,85 +478,87 @@ static void process_delete_list(CustomScanState *node)
 }
 
 /*
- * Find the edges connected to the given node. If there is any edges either
- * delete them or throw an error, depending on the detach delete option.
+ * Scans the edge tables and checks if the deleted vertices are connected to
+ * any edge(s). For DETACH DELETE, the connected edges are deleted. Otherwise,
+ * an error is thrown.
  */
-static void find_connected_edges(CustomScanState *node, char *graph_name,
-                                 List *labels, char *var_name, graphid id,
-                                 bool detach_delete)
+static void check_for_connected_edges(CustomScanState *node)
 {
+    ListCell *lc;
     cypher_delete_custom_scan_state *css =
         (cypher_delete_custom_scan_state *)node;
     EState *estate = css->css.ss.ps.state;
-    ListCell *lc;
+    char *graph_name = css->delete_data->graph_name;
 
-    Increment_Estate_CommandId(estate);
-
-    /*
-     * We need to scan through all the edges to see if this vertex has
-     * any edges attached to it.
-     *
-     * XXX: If we implement an on-disc graph storage system. Such as
-     * an adjacency matrix, the performance of this check can be massively
-     * improved. However, right now we have to scan every edge to see if
-     * one has this vertex as a start or end vertex.
-     */
-    foreach(lc, labels)
+    /* scans each label from css->edge_labels */
+    foreach (lc, css->edge_labels)
     {
         char *label_name = lfirst(lc);
         ResultRelInfo *resultRelInfo;
         TableScanDesc scan_desc;
         HeapTuple tuple;
         TupleTableSlot *slot;
 
-        resultRelInfo = create_entity_result_rel_info(estate,
-                                                      graph_name, label_name);
-
+        resultRelInfo = create_entity_result_rel_info(estate, graph_name,
+                                                      label_name);
         scan_desc = table_beginscan(resultRelInfo->ri_RelationDesc,
                                     estate->es_snapshot, 0, NULL);
-
         slot = ExecInitExtraTupleSlot(
             estate, RelationGetDescr(resultRelInfo->ri_RelationDesc),
             &TTSOpsHeapTuple);
 
-        // scan the table
-        while(true)
+        /* for each row */
+        while (true)
         {
-            graphid startid, endid;
+            graphid startid;
+            graphid endid;
             bool isNull;
+            bool found_startid = false;
+            bool found_endid = false;
 
             tuple = heap_getnext(scan_desc, ForwardScanDirection);
 
-            // no more tuples to process, break and scan the next label.
+            /* no more tuples to process, break and scan the next label. */
             if (!HeapTupleIsValid(tuple))
+            {
                 break;
+            }
 
             ExecStoreHeapTuple(tuple, slot, false);
 
-            startid = GRAPHID_GET_DATUM(slot_getattr(slot, Anum_ag_label_edge_table_start_id, &isNull));
-            endid = GRAPHID_GET_DATUM(slot_getattr(slot, Anum_ag_label_edge_table_end_id, &isNull));
+            startid = GRAPHID_GET_DATUM(slot_getattr(
+                slot, Anum_ag_label_edge_table_start_id, &isNull));
+            endid = GRAPHID_GET_DATUM(
+                slot_getattr(slot, Anum_ag_label_edge_table_end_id, &isNull));
+
+            hash_search(css->vertex_id_htab, (void *)&startid, HASH_FIND,
+                        &found_startid);
 
-            if (id == startid || id == endid)
+            if (!found_startid)
             {
-                /*
-                 * We have found an edge that uses the vertex. Either delete the
-                 * edge or throw an error. Depending on whether the DETACH
-                 * option was specified in the query.
-                 */
-                if (detach_delete)
+                hash_search(css->vertex_id_htab, (void *)&endid, HASH_FIND,
+                            &found_endid);
+            }
+
+            if (found_startid || found_endid)
+            {
+                if (css->delete_data->detach)
+                {
                     delete_entity(estate, resultRelInfo, tuple);
+                }
                 else
-                    ereport(ERROR,
-                            (errcode(ERRCODE_INTERNAL_ERROR),
-                             errmsg("Cannot delete vertex %s, because it still has edges attached. "
-                                    "To delete this vertex, you must first delete the attached edges.",
-                                    var_name)));
+                {
+                    ereport(
+                        ERROR,
+                        (errcode(ERRCODE_INTERNAL_ERROR),
+                         errmsg(
+                             "Cannot delete a vertex that has edge(s). "
+                             "Delete the edge(s) first, or try DETACH DELETE.")));
+                }
             }
         }
 
         table_endscan(scan_desc);
         destroy_entity_result_rel_info(resultRelInfo);
     }
-
-    Decrement_Estate_CommandId(estate);
 }