Deedglass blog: posts about PostgreSQL https://deedglass.com/blog Tested PostgreSQL posts about AI agents that write to a database: roles, row-level security, triggers and the change log. en Fri, 30 Oct 2026 00:00:00 GMT How to govern Medplum FHIR agent writes https://deedglass.com/blog/govern-medplum-fhir-agent-writes https://deedglass.com/blog/govern-medplum-fhir-agent-writes Fri, 30 Oct 2026 00:00:00 GMT Arjun Prabhakaran PostgreSQL How to connect AI agents to Medplum FHIR APIs via Deedglass, enforce pre-write approval rules, and verify committed resource versions in PostgreSQL. How to govern NVIDIA Nemotron database agents https://deedglass.com/blog/govern-nvidia-nemotron-database-agents https://deedglass.com/blog/govern-nvidia-nemotron-database-agents Fri, 30 Oct 2026 00:00:00 GMT Arjun Prabhakaran PostgreSQL How to connect NVIDIA Nemotron reasoning models to PostgreSQL tools via MCP, enforce SQL policies before execution, and verify row diffs with Deedglass. How to govern LlamaIndex database agent tool calls https://deedglass.com/blog/llamaindex-agent-database-tool-approvals https://deedglass.com/blog/llamaindex-agent-database-tool-approvals Fri, 30 Oct 2026 00:00:00 GMT Arjun Prabhakaran PostgreSQL How to give a LlamaIndex FunctionAgent database tools via MCP, enforce pre-write approval policies, and verify real Postgres row changes. The best Postgres MCP server depends on its brakes: five compared https://deedglass.com/blog/best-postgres-mcp-server https://deedglass.com/blog/best-postgres-mcp-server Mon, 26 Oct 2026 00:00:00 GMT Arjun Prabhakaran PostgreSQL Supabase, Neon, Prisma, Postgres MCP Pro and the archived reference server, compared on read-only mode, scoping, confirmations and production advice. drizzle-kit push --force deleted data: why it happens and how to stop it https://deedglass.com/blog/drizzle-kit-push-force-data-loss https://deedglass.com/blog/drizzle-kit-push-force-data-loss Mon, 26 Oct 2026 00:00:00 GMT Arjun Prabhakaran PostgreSQL drizzle-kit push --force accepts every data-loss statement without asking. Why agents reach for it, what it can drop, and a safer push or migrate workflow. How to dry-run an UPDATE before an AI agent commits it https://deedglass.com/blog/dry-run-an-update-before-the-agent-commits https://deedglass.com/blog/dry-run-an-update-before-the-agent-commits Mon, 26 Oct 2026 00:00:00 GMT Arjun Prabhakaran PostgreSQL EXPLAIN guesses how many rows an UPDATE touches; BEGIN and ROLLBACK counts them, but triggers still run and sequences move. A tested dry run. How to enable logical replication on Supabase, Neon, RDS, Cloud SQL and Azure https://deedglass.com/blog/enable-logical-replication-supabase-neon-rds https://deedglass.com/blog/enable-logical-replication-supabase-neon-rds Mon, 26 Oct 2026 00:00:00 GMT Arjun Prabhakaran PostgreSQL How to set wal_level = logical on Supabase, Neon, RDS, Cloud SQL and Azure, who needs REPLICATION, and how to stop slots filling the disk. INSERT … ON CONFLICT said 12 rows. Five of them were overwrites. https://deedglass.com/blog/insert-on-conflict-how-many-rows-updated https://deedglass.com/blog/insert-on-conflict-how-many-rows-updated Mon, 26 Oct 2026 00:00:00 GMT Arjun Prabhakaran PostgreSQL Postgres answers INSERT 0 12 whether an upsert inserted 12 rows or overwrote 5. Count inserts and updates with RETURNING old or MERGE, tested. How to let an AI agent write database migrations without letting it run them https://deedglass.com/blog/let-ai-agents-write-migrations-safely https://deedglass.com/blog/let-ai-agents-write-migrations-safely Mon, 26 Oct 2026 00:00:00 GMT Arjun Prabhakaran PostgreSQL Agents are good at writing migrations and risky at running them. A workflow: the agent writes the file, a person reviews it, CI applies it. PostgreSQL 18 RETURNING OLD and NEW: what it returns, with tested examples https://deedglass.com/blog/postgres-18-returning-old-new https://deedglass.com/blog/postgres-18-returning-old-new Mon, 26 Oct 2026 00:00:00 GMT Arjun Prabhakaran PostgreSQL PostgreSQL 18 lets RETURNING show old and new values in INSERT, UPDATE, DELETE and MERGE. Tested examples, and how to record what a write changed. Hide personal data columns from an AI agent with Postgres column grants https://deedglass.com/blog/postgres-column-grants-hide-pii-from-agent https://deedglass.com/blog/postgres-column-grants-hide-pii-from-agent Mon, 26 Oct 2026 00:00:00 GMT Arjun Prabhakaran PostgreSQL Postgres column-level grants keep an AI agent away from email, phone and other personal data in a table it still needs. A tested setup and its limits. Postgres default privileges and an AI agent's role: new tables, granted or not https://deedglass.com/blog/postgres-default-privileges-for-agent-roles https://deedglass.com/blog/postgres-default-privileges-for-agent-roles Mon, 26 Oct 2026 00:00:00 GMT Arjun Prabhakaran PostgreSQL GRANT ON ALL TABLES misses tables created later; ALTER DEFAULT PRIVILEGES covers them, sensitive ones included. A tested run, and a safer grant plan. Block DROP TABLE and ALTER TABLE for an AI agent's role with a Postgres event trigger https://deedglass.com/blog/postgres-event-trigger-block-ddl https://deedglass.com/blog/postgres-event-trigger-block-ddl Mon, 26 Oct 2026 00:00:00 GMT Arjun Prabhakaran PostgreSQL A Postgres event trigger can refuse DROP and ALTER TABLE from an agent role, even on tables it owns. Tested on PostgreSQL 18, plus the gap: TRUNCATE. Postgres SET ROLE per user: making an AI agent query as the person it serves https://deedglass.com/blog/postgres-set-role-per-user-agent https://deedglass.com/blog/postgres-set-role-per-user-agent Mon, 26 Oct 2026 00:00:00 GMT Arjun Prabhakaran PostgreSQL Run an AI agent's queries as each end user with SET LOCAL ROLE and a per-request setting, so row-level security applies. A tested pattern and its limit. Your Postgres view bypasses row-level security. Here's the fix. https://deedglass.com/blog/postgres-view-bypasses-rls https://deedglass.com/blog/postgres-view-bypasses-rls Mon, 26 Oct 2026 00:00:00 GMT Arjun Prabhakaran PostgreSQL A Postgres view runs with its owner's rights, so it can skip row-level security. A local test, the one-line fix, and a query to find every such view. rds_superuser and neon_superuser: what your agent inherits, and what to give it instead https://deedglass.com/blog/rds-superuser-neon-superuser-agents https://deedglass.com/blog/rds-superuser-neon-superuser-agents Mon, 26 Oct 2026 00:00:00 GMT Arjun Prabhakaran PostgreSQL The default admin roles on RDS, Neon and Supabase can create roles and much more. What each holds, a local SET ROLE test, and a role for agents. A replication slot is filling your disk with WAL: find it, cap it, drop it https://deedglass.com/blog/replication-slot-wal-disk-full https://deedglass.com/blog/replication-slot-wal-disk-full Mon, 26 Oct 2026 00:00:00 GMT Arjun Prabhakaran PostgreSQL An unread Postgres replication slot keeps WAL with no limit by default and can fill the disk. Spot it, cap it with max_slot_wal_keep_size, drop it. How to restore one Postgres table to a point in time https://deedglass.com/blog/restore-one-postgres-table-point-in-time https://deedglass.com/blog/restore-one-postgres-table-point-in-time Mon, 26 Oct 2026 00:00:00 GMT Arjun Prabhakaran PostgreSQL Postgres point-in-time recovery restores a whole cluster, not one table. How to recover a side copy, pause before the bad commit, and copy one table back. Text-to-SQL benchmarks: what BIRD and Spider 2.0 say about letting agents write SQL https://deedglass.com/blog/text-to-sql-benchmarks-bird-spider https://deedglass.com/blog/text-to-sql-benchmarks-bird-spider Mon, 26 Oct 2026 00:00:00 GMT Arjun Prabhakaran PostgreSQL BIRD and Spider 2.0 test whether models turn questions into correct SQL on real databases. Their scores, what execution accuracy hides, and safe setups. The transfer failed halfway and the agent said no money moved. The debit had committed. https://deedglass.com/blog/transfer-failed-halfway-debit-committed https://deedglass.com/blog/transfer-failed-halfway-debit-committed Mon, 26 Oct 2026 00:00:00 GMT Arjun Prabhakaran PostgreSQL An AI agent's transfer failed on the second statement and it reported no money moved. The debit had committed. Why, how to reproduce it, and how to fix it. Why a regex can't block DROP TABLE from an AI agent: a six-statement test https://deedglass.com/blog/why-regex-cant-block-drop-table https://deedglass.com/blog/why-regex-cant-block-drop-table Mon, 26 Oct 2026 00:00:00 GMT Arjun Prabhakaran PostgreSQL We tested a DROP TABLE regex on six statements. Five dropped a table and got through; the only one it blocked was harmless. What to use instead: a parser. An AI agent ran prisma migrate reset on production. What actually stops it? https://deedglass.com/blog/ai-agent-ran-prisma-migrate-reset-on-production https://deedglass.com/blog/ai-agent-ran-prisma-migrate-reset-on-production Sun, 25 Oct 2026 00:00:00 GMT Arjun Prabhakaran PostgreSQL Prisma stops detected AI agents before migrate reset and db push --force-reset. We tested where that check stops, and the role that held when it did. An AI agent retried a timed-out write and it ran twice: how to make retries safe https://deedglass.com/blog/ai-agent-retried-and-wrote-twice https://deedglass.com/blog/ai-agent-retried-and-wrote-twice Sun, 25 Oct 2026 00:00:00 GMT Arjun Prabhakaran PostgreSQL A client timeout doesn't undo a write. Measured on Postgres: the first try commits, then the retry commits again. The idempotency key that stops it. Your AI agent ran an UPDATE without a WHERE. How do you stop the next one? https://deedglass.com/blog/ai-agent-update-without-where https://deedglass.com/blog/ai-agent-update-without-where Sun, 25 Oct 2026 00:00:00 GMT Arjun Prabhakaran PostgreSQL Postgres has no setting that refuses an UPDATE with no WHERE. Five guards compared on real runs, a 20-line trigger that caps agent writes, and recovery. ON DELETE CASCADE deleted more rows than expected: how to see it coming https://deedglass.com/blog/on-delete-cascade-deleted-more-rows https://deedglass.com/blog/on-delete-cascade-deleted-more-rows Sun, 25 Oct 2026 00:00:00 GMT Arjun Prabhakaran PostgreSQL Postgres answered DELETE 1 and 49 rows were gone. Why the command tag skips cascades, how to map every chain, and how to count a delete before it commits. The Postgres MCP server read-only bypass: reproduced, and what actually holds https://deedglass.com/blog/postgres-mcp-server-read-only-bypass https://deedglass.com/blog/postgres-mcp-server-read-only-bypass Sun, 25 Oct 2026 00:00:00 GMT Arjun Prabhakaran PostgreSQL A stacked COMMIT; ends the archived Postgres MCP server's read-only transaction. We reproduced it with psql and tested five fixes. Two hold. Your AI agent said it updated 1 row. Postgres changed 301. https://deedglass.com/blog/agent-said-1-row-postgres-changed-301 https://deedglass.com/blog/agent-said-1-row-postgres-changed-301 Wed, 14 Oct 2026 00:00:00 GMT Arjun Prabhakaran PostgreSQL A real run: an agent's one-row UPDATE fires a legacy trigger, Postgres commits 301 rows, and the tool reports 1. How to see it, and how to put it back. How to give an AI agent safe Postgres access: the role, RLS and statement limits https://deedglass.com/blog/safe-postgres-access-for-ai-agents https://deedglass.com/blog/safe-postgres-access-for-ai-agents Wed, 14 Oct 2026 00:00:00 GMT Arjun Prabhakaran PostgreSQL A tested setup for an AI agent's Postgres access: a narrow role, row-level security per customer, statement and lock limits, and the gap they all share.