dba queries

DBA.md

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+## Inspect page density and TOAST usage
+Shows how many rows fit on pages and how TOAST is used.
+
+The related tunings are:
+* configure `toast_tuple_target`
+* configure ```STORAGE PLAIN/MAIN/EXTENDED/EXTERNAL```
+* order of columns in the table
+
+```sql
+SELECT
+  pgsut.schemaname as schema_name,
+  pgsut.relname as table_name,
+  pg_size_pretty(pg_relation_size(pg_class.oid)) main_size,
+  pg_size_pretty(pg_relation_size(reltoastrelid)) toast_size,
+  n_live_tup,
+  pg_relation_size(pg_class.oid)/(n_live_tup+n_dead_tup) main_avg_size,
+  pg_relation_size(reltoastrelid)/(n_live_tup+n_dead_tup) toast_avg_size,
+  (select option_value::int FROM pg_options_to_table(reloptions) WHERE option_name='toast_tuple_target') as toast_tuple_target
+FROM pg_class
+INNER JOIN pg_namespace ns on relnamespace = ns.oid   
+INNER JOIN pg_stat_user_tables pgsut ON pgsut.relid=pg_class.oid
+WHERE (n_live_tup+n_dead_tup)>0
+AND nspname='banking_stage_results_2'
+ORDER BY 1,2
+```