Databases
PostgreSQL
pg_stat_user_tables for write activity, pg_proc for function bodies, pg_stat_activity for live blocking.
PostgreSQL exposes more useful counters than SQL Server does, and exposes them more
honestly. pg_stat_user_tables carries per-table insert, update and delete counts
that survive as long as the statistics collector does, which makes runtime topology discovery
unusually reliable here.
The catch is that most PostgreSQL ETL is not in PostgreSQL. Where SQL Server estates keep logic in stored procedures, Postgres estates tend to keep it in an external service or a transformation tool, so the database is a strong source for targets and volumes and a weaker one for transformation logic.
What Decim reads from PostgreSQL
Every item below is read-only, and each is a specific view, endpoint or file rather than a category of access. If something here is unacceptable in your environment, it can be removed from the query catalogue — see the agent for how that works.
| What | From | Why it matters |
|---|---|---|
| Write activity | pg_stat_user_tables | n_tup_ins, n_tup_upd, n_tup_del per table |
| Live row estimate | pg_class.reltuples | Cheap approximate counts without scanning |
| Function bodies | pg_proc.prosrc | PL/pgSQL logic where it exists |
| Dependency edges | pg_depend, pg_rewrite | View and function dependencies |
| Live contention | pg_stat_activity, pg_locks | Blocking chains during a stall |
| Column metadata | information_schema.columns | Types and nullability |
| Table sizes | pg_total_relation_size() | Growth anomalies over time |
Permissions required
Written out in full, because "read-only access" is not a specification. Nothing below grants the ability to write, and row access is requested only on the specific tables you name.
CREATE ROLE decim_agent LOGIN PASSWORD '...';
-- Catalog and statistics views are readable by default.
GRANT CONNECT ON DATABASE sales TO decim_agent;
GRANT USAGE ON SCHEMA public TO decim_agent;
-- pg_stat_activity shows other sessions' queries only with this role
-- (PostgreSQL 10+). Without it, query text from other users is NULL.
GRANT pg_read_all_stats TO decim_agent;
-- Reconciliation tables, named explicitly.
GRANT SELECT ON public.intake_batch TO decim_agent;
GRANT SELECT ON public.rejected_transactions TO decim_agent;
-- Never granted: write privileges, or blanket SELECT on the schema.
ALTER DEFAULT PRIVILEGES IN SCHEMA public
REVOKE ALL ON TABLES FROM decim_agent;What it builds
What this source contributes to the pipeline topology and to the evidence available during an investigation:
- Target nodes and their write volumes from the statistics collector
- Transform nodes where PL/pgSQL functions carry logic
- View dependency edges from pg_depend
- Contention evidence from live blocking chains
Nodes learned from a definition are marked declared; nodes observed running are marked observed; nodes both declared and observed are verified. Where two sources disagree, the disagreement is recorded as a drift note rather than resolved silently.
Failure modes it surfaces
What this source is uniquely good at proving — and, just as usefully, at disproving. An investigation that can refute a hypothesis cheaply is worth as much as one that confirms it.
| Failure mode | The signal |
|---|---|
| Load wrote nothing | n_tup_ins flat across the window |
| Duplicate load | n_tup_ins at roughly double the baseline |
| Blocking during a stall | Blocking chain in pg_stat_activity |
| Autovacuum starvation | last_autovacuum far behind n_dead_tup |
Limits
What this integration cannot tell you. Stated because an investigation that overstates its sources produces confident wrong answers, which is worse than an honest blocked.
- Statistics counters reset on
pg_stat_reset()and do not survive a crash-recovery restart - Transformation logic usually lives outside the database, so this source alone rarely yields transform nodes
reltuplesis an estimate refreshed by ANALYZE — never cite it as an exact count
Related integrations
- SQL Server — Reads catalog metadata, procedure bodies and write activity — the definitions git never sees.
- Apache Airflow — The metadata database holds connections, variables, pools and manual state — none of it in git.
- dbt — manifest.json is the model graph; run_results.json is what actually happened. Both are artefacts, not APIs.
See all integrations, or how the sources are combined into one graph.
Get started
Investigating a PostgreSQL pipeline?
Bring an incident you already know the answer to. If Decim gets it wrong, that is a more useful demo than one where it doesn't.