Make age extension usable from shared_preload_libraries

[serdarmumcu]

When AGE is loaded via shared_preload_libraries, its hooks (post_parse_analyze, set_rel_pathlist, object_access) are active before CREATE EXTENSION age is run. This causes errors when non-Cypher queries trigger those hooks and ag_catalog does not yet exist.

Changes

• Add is_age_extension_exist() with a relcache callback cache so that checking pg_extension is not repeated on every hook invocation.
• Guard post_parse_analyze, set_rel_pathlist, and object_access hooks with is_age_extension_exist() so they become no-ops when the extension is not installed.
• Refactor ag_ProcessUtility_hook to detect CREATE/DROP EXTENSION age and broadcast a relcache invalidation via CacheInvalidateRelcacheByRelid(ExtensionRelationId) so other backends update their cached extension state.
• Wrap DROP EXTENSION processing in PG_TRY/PG_CATCH to restore object_access_hook if the drop fails (e.g. dependent objects).
• Skip _PG_init during pg_upgrade (IsBinaryUpgrade) to avoid hook registration when the binary-upgrade machinery is running.
• Add regression tests that verify hooks do not error when ag_catalog schema is absent.

[jrgemignani]

@serdarmumcu The build has an error -

This needs to be fixed.

[Copilot]

Pull request overview

This PR makes the AGE shared library safe to load via shared_preload_libraries by ensuring its hooks become no-ops until the age extension is actually installed, avoiding failures when ag_catalog doesn’t exist yet.

Changes:

• Adds a cached pg_extension existence check and uses it to guard key hooks (post_parse_analyze, set_rel_pathlist, object_access).
• Updates ProcessUtility hook logic to detect CREATE/DROP EXTENSION age, invalidate the cached state across backends, and safely restore hooks on failure.
• Extends regression coverage to validate hook behavior when ag_catalog is absent and improves cleanup in VLE regression SQL.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/include/catalog/ag_catalog.h	Exposes the new AGE-extension existence check API.
src/backend/parser/cypher_analyze.c	Guards post-parse analysis hook when AGE extension isn’t installed.
src/backend/optimizer/cypher_paths.c	Guards planner hook when AGE extension isn’t installed.
src/backend/catalog/ag_catalog.c	Implements extension-existence caching, hook guarding, and cross-backend invalidation on create/drop.
src/backend/age.c	Skips _PG_init during binary upgrade to avoid hook registration during pg_upgrade.
regress/sql/drop.sql	Adds regression coverage for hook safety when ag_catalog is missing.
regress/sql/cypher_vle.sql	Adds missing cleanup for helper functions created during the test.
regress/expected/drop.out / regress/expected/cypher_vle.out	Updates expected outputs to match the new regression behavior.

Comments suppressed due to low confidence (1)

src/backend/catalog/ag_catalog.c:272

• drop_age_extension() is now unused (no remaining call sites). With the project building with COPT=-Werror in CI, an unused static function is likely to trigger -Wunused-function and fail the build; the forward declaration at the top should be removed as well.

static void drop_age_extension(DropStmt *stmt)
{
    /* Remove all graphs */
    drop_graphs(get_graphnames());

    /* Remove the object access hook */
    object_access_hook_fini();

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[serdarmumcu]

@serdarmumcu The build has an error -

This needs to be fixed.

@jrgemignani Fixed — removed the dead drop_age_extension() function and also cleaned up unrelated changes from internal branches that had leaked into the PR. The commit now only contains changes related to shared_preload_libraries support. Ready for re-review.