rafsun42 opened a new issue, #1446:
URL: https://github.com/apache/age/issues/1446
**Describe the bug**
In a chained MERGE query with two MERGE clauses, the first MERGE does not
see the updates of the second one.
**What data setup do we need to do?**
```pgsql
SELECT create_graph('breakmerge');
SELECT * FROM cypher('breakmerge', $$
CREATE (:A), (:C)
$$) as (a agtype);
```
**What is the command that caused the error?**
```pgsql
SELECT * FROM cypher('breakmerge', $$
MATCH (x)
MERGE (x)-[:r]->(:t)
MERGE (:C)-[:r]->(:t)
$$) as (a agtype);
```
Outputs:
```
a
------------------------------------------------------------------
{"id": 844424930131969, "label": "A", "properties": {}}::vertex
{"id": 1125899906842625, "label": "C", "properties": {}}::vertex
{"id": 1125899906842626, "label": "C", "properties": {}}::vertex
{"id": 1125899906842627, "label": "C", "properties": {}}::vertex
(4 rows)
```
**Expected behavior**
There should be only one instance of `:A` and `:C` (verified in Neo4j).
```
a
------------------------------------------------------------------
{"id": 844424930131969, "label": "A", "properties": {}}::vertex
{"id": 1125899906842625, "label": "C", "properties": {}}::vertex
```
**Environment (please complete the following information):**
Master branch; PG 15.4
**Additional context**
Maybe related to how command IDs are used in MERGE's executor.
My assumption: when the MATCH node sends `:A` to the first MERGE node it
creates `(:A)-[:r]->(:t)` and the second MERGE node creates `(:C)-[:r]->(:t)`.
In the next iteration, MATCH sends `:C` to the first MERGE, but it does not see
that the second MERGE has already created `(:C)-[:r]->(:t)` in the previous
iteration.
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