age_global_graph: stabilize regression tests

[jrgemignani]

age_global_graph: stabilize regression tests under concurrent xid load

Wrap both vertex_stats() context-building phases in a single BEGIN ISOLATION LEVEL REPEATABLE READ; ... COMMIT; transaction so the three calls share one snapshot. This prevents the snapshot-fallback path in is_ggctx_invalid() from purging an already-built graph context when concurrent xid activity (autovacuum, parallel installcheck, replication, shared CI) advances the snapshot between calls, which would otherwise make the targeted delete_global_graphs(name) checks return false instead of the expected true. Read Committed is insufficient because it acquires a fresh snapshot per statement; REPEATABLE READ pins one snapshot for the whole transaction.

Also add explicit ORDER BY id to the three direct-SQL label-table SELECTs (_ag_label_vertex x2, _ag_label_edge) that return multiple rows, so their output no longer depends on heap scan order.

This is a test-only change (regress/sql/age_global_graph.sql and regress/expected/age_global_graph.out); no extension C code or SQL is modified.

All 37 regression tests pass (installcheck) on PostgreSQL 18.3.

Co-authored-by: GitHub Copilot noreply@github.com

modified: regress/expected/age_global_graph.out
modified: regress/sql/age_global_graph.sql

[Copilot]

Pull request overview

This PR stabilizes the age_global_graph regression test output under concurrent transaction ID (xid) churn by making the snapshot used during graph-context construction deterministic, and by ensuring multi-row heap reads are ordered.

Changes:

• Wrap each 3-call vertex_stats() context build phase in a single BEGIN ISOLATION LEVEL REPEATABLE READ; ... COMMIT; transaction so the calls share one snapshot.
• Add ORDER BY id to direct SQL reads from _ag_label_vertex and _ag_label_edge to avoid nondeterministic heap-scan ordering.
• Update the expected regression output to match the new SQL (transaction statements + ordered SELECT output).

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
regress/sql/age_global_graph.sql	Pins a single snapshot per context-build phase via REPEATABLE READ and makes label-table SELECT ordering deterministic.
regress/expected/age_global_graph.out	Updates expected output to reflect the added transaction statements and ordered SELECT results.

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