feat(s3): add workload profile by query type

New s3 report groups pg_stat_statements by first SQL keyword
(SELECT, INSERT, UPDATE, DELETE, etc.) to show workload composition.

The tricky part: SQL comments before the keyword. The regex:
1. Strips block comments: /* ... */ (including multi-line)
2. Strips leading line comments: -- ... (including chained)
3. Extracts first remaining word as the query type

Shows per-type: calls, calls%, exec time, exec%, plan time,
avg time per call, and row count.

PG13+ path uses total_exec_time/total_plan_time split.
Older PG path uses total_time.

Closes #37

Author: NikolayS

README.md

@@ -64,6 +64,7 @@ Then connect to any Postgres server via psql and type `:dba` to open the interac
 |----|--------|
 | s1 | Slowest queries by total time (requires `pg_stat_statements`) |
 | s2 | Slowest queries report (requires `pg_stat_statements`) |
+| s3 | Workload profile by query type (requires `pg_stat_statements`) |
 
 ### Configuration and other
 | ID | Report |

sql/s3_pg_stat_statements_workload.sql

@@ -0,0 +1,73 @@
+-- Workload profile by query type (requires pg_stat_statements)
+
+-- Groups pg_stat_statements entries by first SQL keyword.
+-- Strips block comments (/* ... */) and line comments (-- ...)
+-- before extracting the keyword.
+
+\if :postgres_dba_pgvers_13plus
+with data as (
+  select
+    lower((regexp_match(
+      regexp_replace(
+        regexp_replace(query, '/\*.*?\*/', '', 'gs'),
+        '^\s*(--[^\n]*\n\s*)*', '', 'g'
+      ),
+      '^\s*(\w+)'
+    ))[1]) as word,
+    calls,
+    total_exec_time,
+    total_plan_time,
+    rows
+  from pg_stat_statements
+)
+select
+  coalesce(word, '???') as "Query Type",
+  sum(calls) as "Calls",
+  round(
+    100.0 * sum(calls) / nullif(sum(sum(calls)) over (), 0), 1
+  ) as "Calls %",
+  round(sum(total_exec_time)::numeric, 1) as "Exec (ms)",
+  round(
+    100.0 * sum(total_exec_time) / nullif(sum(sum(total_exec_time)) over (), 0), 1
+  ) as "Exec %",
+  round(sum(total_plan_time)::numeric, 1) as "Plan (ms)",
+  round(
+    (sum(total_exec_time) / nullif(sum(calls), 0))::numeric, 3
+  ) as "Avg (ms/call)",
+  sum(rows) as "Rows"
+from data
+group by word
+order by sum(total_exec_time) desc;
+\else
+with data as (
+  select
+    lower((regexp_match(
+      regexp_replace(
+        regexp_replace(query, '/\*.*?\*/', '', 'gs'),
+        '^\s*(--[^\n]*\n\s*)*', '', 'g'
+      ),
+      '^\s*(\w+)'
+    ))[1]) as word,
+    calls,
+    total_time,
+    rows
+  from pg_stat_statements
+)
+select
+  coalesce(word, '???') as "Query Type",
+  sum(calls) as "Calls",
+  round(
+    100.0 * sum(calls) / nullif(sum(sum(calls)) over (), 0), 1
+  ) as "Calls %",
+  round(sum(total_time)::numeric, 1) as "Time (ms)",
+  round(
+    100.0 * sum(total_time) / nullif(sum(sum(total_time)) over (), 0), 1
+  ) as "Time %",
+  round(
+    (sum(total_time) / nullif(sum(calls), 0))::numeric, 3
+  ) as "Avg (ms/call)",
+  sum(rows) as "Rows"
+from data
+group by word
+order by sum(total_time) desc;
+\endif

start.psql

@@ -24,6 +24,7 @@
 \echo '  r2 – Alter user with random password (interactive)'
 \echo '  s1 – Slowest queries, by total time (requires pg_stat_statements)'
 \echo '  s2 – Slowest queries report (requires pg_stat_statements)'
+\echo '  s3 – Workload profile by query type (requires pg_stat_statements)'
 \echo '  t1 – Postgres parameters tuning'
 \echo '  t2 – Objects with custom storage parameters'
 \echo '  v1 – Vacuum: current activity'
@@ -58,6 +59,7 @@ select
 :d_stp::text = 'r2' as d_step_is_r2,
 :d_stp::text = 's1' as d_step_is_s1,
 :d_stp::text = 's2' as d_step_is_s2,
+:d_stp::text = 's3' as d_step_is_s3,
 :d_stp::text = 't1' as d_step_is_t1,
 :d_stp::text = 't2' as d_step_is_t2,
 :d_stp::text = 'v1' as d_step_is_v1,
@@ -162,6 +164,10 @@ select
   \ir ./sql/s2_pg_stat_statements_report.sql
   \prompt 'Press <Enter> to continue…' d_dummy
   \ir ./start.psql
+\elif :d_step_is_s3
+  \ir ./sql/s3_pg_stat_statements_workload.sql
+  \prompt 'Press <Enter> to continue…' d_dummy
+  \ir ./start.psql
 \elif :d_step_is_t1
   \ir ./sql/t1_tuning.sql
   \prompt 'Press <Enter> to continue…' d_dummy