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new d0741d8d Fix entity_exists() CID visibility for CREATE + WITH + MERGE
(#2343)
d0741d8d is described below
commit d0741d8dc90f0c2f636f049b48b9d41eb54516cf
Author: Greg Felice <[email protected]>
AuthorDate: Mon Mar 2 13:09:19 2026 -0500
Fix entity_exists() CID visibility for CREATE + WITH + MERGE (#2343)
* Fix entity_exists() CID visibility for CREATE + WITH + MERGE (#1954)
When a Cypher query chains CREATE ... WITH ... MERGE, vertices created
by CREATE become invisible to entity_exists() after a threshold number
of input rows. This causes MERGE to throw "vertex assigned to variable
was deleted".
Root cause: CREATE calls CommandCounterIncrement() which advances the
global command ID, but does not update es_snapshot->curcid. The
Decrement/Increment CID macros used by the executors bring curcid back
to the same value on each iteration. After enough rows, newly inserted
vertices have a Cmin >= curcid and HeapTupleSatisfiesMVCC rejects them
(requires Cmin < curcid).
Fix: In entity_exists(), temporarily set es_snapshot->curcid to the
current global command ID (via GetCurrentCommandId) for the duration
of the scan, then restore it. This makes all entities inserted by
preceding clauses in the same query visible to the existence check.
Co-Authored-By: Claude Opus 4.6 <[email protected]>
* Use Max() to prevent curcid regression in entity_exists()
Address review feedback: es_snapshot->curcid can be ahead of the
global CID due to Increment_Estate_CommandId macros. Unconditionally
assigning GetCurrentCommandId(false) could decrease curcid, making
previously visible tuples invisible. Use Max(saved_curcid,
GetCurrentCommandId(false)) to ensure we only ever increase visibility.
Co-Authored-By: Claude Opus 4.6 <[email protected]>
---------
Co-authored-by: Claude Opus 4.6 <[email protected]>
---
regress/expected/cypher_merge.out | 130 ++++++++++++++++++++++++++++++++++++
regress/sql/cypher_merge.sql | 65 ++++++++++++++++++
src/backend/executor/cypher_utils.c | 21 ++++++
3 files changed, 216 insertions(+)
diff --git a/regress/expected/cypher_merge.out
b/regress/expected/cypher_merge.out
index 8c37dc2d..4242f2f5 100644
--- a/regress/expected/cypher_merge.out
+++ b/regress/expected/cypher_merge.out
@@ -1865,6 +1865,114 @@ $$) AS (edge_count agtype);
0
(1 row)
+-- Issue 1954: CREATE + WITH + MERGE causes "vertex was deleted" error
+-- when the number of input rows exceeds the snapshot's command ID window.
+-- entity_exists() used a stale curcid, making recently-created vertices
+-- invisible on later iterations.
+--
+SELECT * FROM create_graph('issue_1954');
+NOTICE: graph "issue_1954" has been created
+ create_graph
+--------------
+
+(1 row)
+
+-- Setup: create source nodes and relationships (3 rows to trigger the bug)
+SELECT * FROM cypher('issue_1954', $$
+ CREATE (:A {name: 'a1'})-[:R]->(:B {name: 'b1'}),
+ (:A {name: 'a2'})-[:R]->(:B {name: 'b2'}),
+ (:A {name: 'a3'})-[:R]->(:B {name: 'b3'})
+$$) AS (result agtype);
+ result
+--------
+(0 rows)
+
+-- This query would fail with "vertex assigned to variable c was deleted"
+-- on the 3rd row before the fix.
+SELECT * FROM cypher('issue_1954', $$
+ MATCH (a:A)-[:R]->(b:B)
+ CREATE (c:C {name: a.name + '|' + b.name})
+ WITH a, b, c
+ MERGE (a)-[:LINK]->(c)
+ RETURN a.name, b.name, c.name
+ ORDER BY a.name
+$$) AS (a agtype, b agtype, c agtype);
+ a | b | c
+------+------+---------
+ "a1" | "b1" | "a1|b1"
+ "a2" | "b2" | "a2|b2"
+ "a3" | "b3" | "a3|b3"
+(3 rows)
+
+-- Verify edges were created
+SELECT * FROM cypher('issue_1954', $$
+ MATCH (a:A)-[:LINK]->(c:C)
+ RETURN a.name, c.name
+ ORDER BY a.name
+$$) AS (a agtype, c agtype);
+ a | c
+------+---------
+ "a1" | "a1|b1"
+ "a2" | "a2|b2"
+ "a3" | "a3|b3"
+(3 rows)
+
+-- Test with two MERGEs (more complex case from the original report)
+SELECT * FROM cypher('issue_1954', $$
+ MATCH ()-[e:LINK]->() DELETE e
+$$) AS (result agtype);
+ result
+--------
+(0 rows)
+
+SELECT * FROM cypher('issue_1954', $$
+ MATCH (c:C) DELETE c
+$$) AS (result agtype);
+ result
+--------
+(0 rows)
+
+SELECT * FROM cypher('issue_1954', $$
+ MATCH (a:A)-[:R]->(b:B)
+ CREATE (c:C {name: a.name + '|' + b.name})
+ WITH a, b, c
+ MERGE (a)-[:LINK1]->(c)
+ MERGE (b)-[:LINK2]->(c)
+ RETURN a.name, b.name, c.name
+ ORDER BY a.name
+$$) AS (a agtype, b agtype, c agtype);
+ a | b | c
+------+------+---------
+ "a1" | "b1" | "a1|b1"
+ "a2" | "b2" | "a2|b2"
+ "a3" | "b3" | "a3|b3"
+(3 rows)
+
+-- Verify both sets of edges
+SELECT * FROM cypher('issue_1954', $$
+ MATCH (a:A)-[:LINK1]->(c:C)
+ RETURN a.name, c.name
+ ORDER BY a.name
+$$) AS (a agtype, c agtype);
+ a | c
+------+---------
+ "a1" | "a1|b1"
+ "a2" | "a2|b2"
+ "a3" | "a3|b3"
+(3 rows)
+
+SELECT * FROM cypher('issue_1954', $$
+ MATCH (b:B)-[:LINK2]->(c:C)
+ RETURN b.name, c.name
+ ORDER BY b.name
+$$) AS (b agtype, c agtype);
+ b | c
+------+---------
+ "b1" | "a1|b1"
+ "b2" | "a2|b2"
+ "b3" | "a3|b3"
+(3 rows)
+
--
-- clean up graphs
--
@@ -1888,6 +1996,11 @@ SELECT * FROM cypher('issue_1446', $$ MATCH (n) DETACH
DELETE n $$) AS (a agtype
---
(0 rows)
+SELECT * FROM cypher('issue_1954', $$ MATCH (n) DETACH DELETE n $$) AS (a
agtype);
+ a
+---
+(0 rows)
+
--
-- delete graphs
--
@@ -1985,6 +2098,23 @@ NOTICE: graph "issue_1446" has been dropped
(1 row)
+SELECT drop_graph('issue_1954', true);
+NOTICE: drop cascades to 9 other objects
+DETAIL: drop cascades to table issue_1954._ag_label_vertex
+drop cascades to table issue_1954._ag_label_edge
+drop cascades to table issue_1954."A"
+drop cascades to table issue_1954."R"
+drop cascades to table issue_1954."B"
+drop cascades to table issue_1954."C"
+drop cascades to table issue_1954."LINK"
+drop cascades to table issue_1954."LINK1"
+drop cascades to table issue_1954."LINK2"
+NOTICE: graph "issue_1954" has been dropped
+ drop_graph
+------------
+
+(1 row)
+
--
-- End
--
diff --git a/regress/sql/cypher_merge.sql b/regress/sql/cypher_merge.sql
index cc900e73..5939c42a 100644
--- a/regress/sql/cypher_merge.sql
+++ b/regress/sql/cypher_merge.sql
@@ -860,6 +860,69 @@ SELECT * FROM cypher('issue_1446', $$
RETURN count(*) AS edge_count
$$) AS (edge_count agtype);
+-- Issue 1954: CREATE + WITH + MERGE causes "vertex was deleted" error
+-- when the number of input rows exceeds the snapshot's command ID window.
+-- entity_exists() used a stale curcid, making recently-created vertices
+-- invisible on later iterations.
+--
+SELECT * FROM create_graph('issue_1954');
+
+-- Setup: create source nodes and relationships (3 rows to trigger the bug)
+SELECT * FROM cypher('issue_1954', $$
+ CREATE (:A {name: 'a1'})-[:R]->(:B {name: 'b1'}),
+ (:A {name: 'a2'})-[:R]->(:B {name: 'b2'}),
+ (:A {name: 'a3'})-[:R]->(:B {name: 'b3'})
+$$) AS (result agtype);
+
+-- This query would fail with "vertex assigned to variable c was deleted"
+-- on the 3rd row before the fix.
+SELECT * FROM cypher('issue_1954', $$
+ MATCH (a:A)-[:R]->(b:B)
+ CREATE (c:C {name: a.name + '|' + b.name})
+ WITH a, b, c
+ MERGE (a)-[:LINK]->(c)
+ RETURN a.name, b.name, c.name
+ ORDER BY a.name
+$$) AS (a agtype, b agtype, c agtype);
+
+-- Verify edges were created
+SELECT * FROM cypher('issue_1954', $$
+ MATCH (a:A)-[:LINK]->(c:C)
+ RETURN a.name, c.name
+ ORDER BY a.name
+$$) AS (a agtype, c agtype);
+
+-- Test with two MERGEs (more complex case from the original report)
+SELECT * FROM cypher('issue_1954', $$
+ MATCH ()-[e:LINK]->() DELETE e
+$$) AS (result agtype);
+SELECT * FROM cypher('issue_1954', $$
+ MATCH (c:C) DELETE c
+$$) AS (result agtype);
+
+SELECT * FROM cypher('issue_1954', $$
+ MATCH (a:A)-[:R]->(b:B)
+ CREATE (c:C {name: a.name + '|' + b.name})
+ WITH a, b, c
+ MERGE (a)-[:LINK1]->(c)
+ MERGE (b)-[:LINK2]->(c)
+ RETURN a.name, b.name, c.name
+ ORDER BY a.name
+$$) AS (a agtype, b agtype, c agtype);
+
+-- Verify both sets of edges
+SELECT * FROM cypher('issue_1954', $$
+ MATCH (a:A)-[:LINK1]->(c:C)
+ RETURN a.name, c.name
+ ORDER BY a.name
+$$) AS (a agtype, c agtype);
+
+SELECT * FROM cypher('issue_1954', $$
+ MATCH (b:B)-[:LINK2]->(c:C)
+ RETURN b.name, c.name
+ ORDER BY b.name
+$$) AS (b agtype, c agtype);
+
--
-- clean up graphs
--
@@ -867,6 +930,7 @@ SELECT * FROM cypher('cypher_merge', $$ MATCH (n) DETACH
DELETE n $$) AS (a agty
SELECT * FROM cypher('issue_1630', $$ MATCH (n) DETACH DELETE n $$) AS (a
agtype);
SELECT * FROM cypher('issue_1709', $$ MATCH (n) DETACH DELETE n $$) AS (a
agtype);
SELECT * FROM cypher('issue_1446', $$ MATCH (n) DETACH DELETE n $$) AS (a
agtype);
+SELECT * FROM cypher('issue_1954', $$ MATCH (n) DETACH DELETE n $$) AS (a
agtype);
--
-- delete graphs
@@ -877,6 +941,7 @@ SELECT drop_graph('issue_1630', true);
SELECT drop_graph('issue_1691', true);
SELECT drop_graph('issue_1709', true);
SELECT drop_graph('issue_1446', true);
+SELECT drop_graph('issue_1954', true);
--
-- End
diff --git a/src/backend/executor/cypher_utils.c
b/src/backend/executor/cypher_utils.c
index eff82992..94028423 100644
--- a/src/backend/executor/cypher_utils.c
+++ b/src/backend/executor/cypher_utils.c
@@ -208,6 +208,7 @@ bool entity_exists(EState *estate, Oid graph_oid, graphid
id)
HeapTuple tuple;
Relation rel;
bool result = true;
+ CommandId saved_curcid;
/*
* Extract the label id from the graph id and get the table name
@@ -219,6 +220,23 @@ bool entity_exists(EState *estate, Oid graph_oid, graphid
id)
ScanKeyInit(&scan_keys[0], 1, BTEqualStrategyNumber,
F_GRAPHIDEQ, GRAPHID_GET_DATUM(id));
+ /*
+ * Temporarily advance the snapshot's curcid so that entities inserted
+ * by preceding clauses (e.g., CREATE) in the same query are visible.
+ * CREATE calls CommandCounterIncrement() which advances the global
+ * CID, but does not update es_snapshot->curcid. The Decrement/Increment
+ * CID macros used by the executors can leave curcid behind the global
+ * CID, making recently created entities invisible to this scan.
+ *
+ * Use Max to ensure we never decrease curcid. The executor macros
+ * (Increment_Estate_CommandId) can push curcid above the global CID,
+ * and blindly assigning GetCurrentCommandId could make tuples that
+ * are visible at the current curcid become invisible.
+ */
+ saved_curcid = estate->es_snapshot->curcid;
+ estate->es_snapshot->curcid = Max(saved_curcid,
+ GetCurrentCommandId(false));
+
rel = table_open(label->relation, RowExclusiveLock);
scan_desc = table_beginscan(rel, estate->es_snapshot, 1, scan_keys);
@@ -236,6 +254,9 @@ bool entity_exists(EState *estate, Oid graph_oid, graphid
id)
table_endscan(scan_desc);
table_close(rel, RowExclusiveLock);
+ /* Restore the original curcid */
+ estate->es_snapshot->curcid = saved_curcid;
+
return result;
}
