fix: Postgres reorganizer crashes due to missing graph-store methods

[Kwizii]

Bug Description

When MOS_ENABLE_REORGANIZE=true and the graph backend is PostgresGraphDB, the background structure optimization thread crashes because several methods exist on Neo4jGraphDB but are missing or incompatible on PostgresGraphDB.

Observed runtime error:

AttributeError: 'PostgresGraphDB' object has no attribute 'node_not_exist'

After that is patched, the next failures are typically get_memory_count, get_edges, or edge_exists(..., direction=..., user_name=...).

Method	Used by	Impact
node_not_exist(scope, user_name)	reorganizer.optimize_structure	Thread crash
get_memory_count(memory_type, user_name)	reorganizer.optimize_structure	AttributeError
get_edges(id, type, direction, user_name)	handler._resolve_in_graph, manager._inherit_edges	MERGED_TO merge cannot inherit edges
edge_exists(..., direction=..., user_name=...)	reorganizer / handler / manager	TypeError or wrong semantics
get_structure_optimization_candidates(..., user_name=...)	reorganizer	Ignores per-user scope
search_by_fulltext(...)	recall / searcher	AttributeError on keyword recall path

How to Reproduce

1. Run MemOS Product API with Postgres graph backend and MOS_ENABLE_REORGANIZE=true.
2. Add memories via /product/add until the reorganizer background thread runs structure optimization.
3. Observe logs from _run_structure_optimization_periodically / optimize_structure.

Environment

• Python: 3.11
• Operating System: Linux (Docker)
• MemOS: main branch
• Graph backend: postgres + pgvector
• MOS_ENABLE_REORGANIZE=true

Additional Context

• Postgres backend should expose the same graph-store interface used by tree text memory reorganizer and handler so redundant-memory merge can create MERGED_TO edges without crashing.
• I am willing to implement this myself and have a patch ready on fork branch fix/postgres-reorganizer-compat (PR fix: PostgresGraphDB reorganizer/handler compatibility #2273).

[Memtensor-AI]

🤖 AutoDev has picked up this issue and started working on it.

Task ID: 06bd58c4de865475
Working branch: bugfix/autodev-2272-20260822153326438
Target branch: latest dev* branch
Workflow: opsp (analysis → coding → testing → PR)

I will post the PR link here once done. If I need more information, I will ask in the comments.

[Memtensor-AI]

✅ AutoDev task 06bd58c4de865475 completed.

Summary: Fixed issue #2272: PostgresGraphDB was missing the graph-store interface used by the tree text memory reorganizer and handler, crashing the background structure optimization thread (AttributeError: 'PostgresGraphDB' object has no attribute 'node_not_exist') when MOS_ENABLE_REORGANIZE=true with graph_db.backend=postgres, and blocking MERGED_TO edge creation during redundant-memory merge.

Changes (all in src/memos/graph_dbs/):

• Added node_not_exist(scope, user_name) and get_memory_count(memory_type, user_name) to PostgresGraphDB.
• Extended edge_exists with type="ANY" (default), direction ("OUT"/"OUTGOING", "IN"/"INCOMING", "ANY") and user_name; the legacy 3-argument call still works and defaults to bidirectional matching.
• Added get_edges(id, type, direction, user_name) to PostgresGraphDB returning [{"from","to","type"}] like Neo4j, plus a default contract on BaseGraphDB; supports the scheduler's direction="OUT" alias.
• get_structure_optimization_candidates now accepts **kwargs and honors the caller's user_name (previously hardcoded to config.user_name, which leaked across users).
• Added search_by_fulltext built on PostgreSQL full-text search (to_tsvector/to_tsquery/ts_rank) with safe word quoting, tsquery_config defaulting to 'simple', and return shape [{"id","score"}] matching the polardb backend; the recall/searcher keyword path no longer raises AttributeError.

Tests: new tests/graph_dbs/test_postgres_graph_db.py with 22 unit tests stubbing psycopg2 (no live DB needed) - all pass. Regression: tests/graph_dbs (53 passed, 3 skipped), tests/memories/textual (60 passed), full suite 743 passed; the only failures are pre-existing and environment-related (missing optional markitdown/qdrant packages, and an unrelated kv-cache bug reproduced on a clean checkout of dev-v2.0.30). ruff check and ruff format are clean.

Committed as 14720c2 on bugfix/autodev-2272-20260822153326438 (pushed to origin) and the opsp artifacts (.ai-tasks task file + openspec proposal/spec/design/tasks/test-cases/verification-report) were synced to the memos-autodev-specs repo.

Base branch: main
Branch: bugfix/autodev-2272-20260822153326438
Commit: 14720c2
PR: #2276
Assigned to: @CarltonXiang
Reviewers: @wustzdy