gregfelice commented on issue #2450:
URL: https://github.com/apache/age/issues/2450#issuecomment-4875513568
Thanks for the clear reproducer, @bilalsp — that made this quick to pin down.
**Root cause.** AGE's CREATE/MERGE/SET paths build the insert/update tuple
slot from the full label-table descriptor but only populate the columns AGE
manages (`id`/`properties` for vertices, `id`/`start_id`/`end_id`/`properties`
for edges). Your `GENERATED ALWAYS ... STORED` column is an extra attribute AGE
never initialized, so `heap_form_tuple()` read the uninitialized slot entry and
segfaulted dereferencing garbage. The same happens for a plain added column,
and on SET as well as CREATE.
**Fix** (PR incoming):
- The entity slot is now null-initialized before AGE fills its own columns,
so any column AGE doesn't manage defaults to NULL instead of stale memory.
- Stored generated columns are computed via `ExecComputeStoredGenerated()`
before the tuple is materialized — on insert (CREATE/MERGE) and recomputed on
update (SET) — matching PostgreSQL semantics.
Verified against your exact repro plus a new regression test: your case now
works and the generated column is correctly computed:
```
CREATE (p:Product {category: 'disk', ...}) --> "Product".category = 'disk'
MATCH (p:Product {category:'disk'}) SET p.category='ssd' --> recomputes to
'ssd'
```
**One caveat worth flagging:** on `SET`, AGE rebuilds the row from
`id`/`properties`, so a *generated* column recomputes correctly, but a *plain*
(non-generated) column would be reset to NULL. If you need a value preserved
across updates, use a `GENERATED ... STORED` column derived from `properties`
(as in your example) rather than a plain column — that path is fully supported.
**Workaround until the PR lands:** if you can't wait, computing `category`
at query time via an expression index instead of a stored generated column
avoids the crash:
```sql
CREATE INDEX ON age_bug."Product" ((agtype_access_operator(properties,
'"category"')));
```
I'll link the PR here shortly.
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