-- 修复 IndexApprovedDocument: ON CONFLICT (chunk_hash) 需要唯一约束
DELETE FROM context_memory_chunks a
USING context_memory_chunks b
WHERE a.chunk_hash IS NOT NULL
  AND a.chunk_hash <> ''
  AND a.chunk_hash = b.chunk_hash
  AND a.id > b.id;

UPDATE context_memory_chunks
SET chunk_hash = 'legacy_empty_' || id::text
WHERE chunk_hash IS NULL OR chunk_hash = '';

DROP INDEX IF EXISTS idx_mem_chunks_hash;
CREATE UNIQUE INDEX IF NOT EXISTS uq_mem_chunks_hash ON context_memory_chunks(chunk_hash);