Keep track of nested queries stack-style and emit parent_query_id

docker/init/00-schema.sql

@@ -53,6 +53,8 @@ CREATE TABLE pg_stat_ch.events_raw
 
     query_id Int64 COMMENT '64-bit hash identifying normalized queries. Queries differing only in constants share the same query_id. Use for aggregating statistics across similar queries.',
 
+    parent_query_id UInt64 COMMENT 'query_id of the calling query (e.g. the plpgsql function that issued this SPI statement). 0 for top-level queries. Use WHERE parent_query_id = 0 to restrict aggregations to top-level queries and avoid double-counting CPU and duration.',
+
     cmd_type LowCardinality(String) COMMENT 'Command type: SELECT, INSERT, UPDATE, DELETE, MERGE, UTILITY, or UNKNOWN. Use for workload characterization (read-heavy vs write-heavy).',
 
     rows UInt64 COMMENT 'Rows returned (SELECT) or affected (INSERT/UPDATE/DELETE). HIGH: large result sets or bulk operations. LOW: point queries. Watch for unexpected HIGH values indicating missing WHERE clauses.',

migrations/001_add_parent_query_id.sql

@@ -0,0 +1,12 @@
+-- Migration: add parent_query_id column
+--
+-- Introduced in pg_stat_ch 0.4.x. Each event now carries the query_id of its
+-- calling query (e.g. the plpgsql function that issued an SPI statement).
+-- Top-level queries emit 0. Use WHERE parent_query_id = 0 in aggregations to
+-- avoid double-counting CPU and duration across nested calls.
+--
+-- Run against your ClickHouse instance before upgrading the extension:
+--   clickhouse-client < migrations/001_add_parent_query_id.sql
+
+ALTER TABLE pg_stat_ch.events_raw
+    ADD COLUMN IF NOT EXISTS parent_query_id UInt64 DEFAULT 0;

src/export/stats_exporter.cc

@@ -93,6 +93,7 @@ void ExportEventStats(const std::vector<PschEvent>& events, StatsExporter* expor
   auto col_username = exporter->DbUserColumn();
   auto col_pid = exporter->RecordInt32("pid");
   auto col_query_id = exporter->RecordInt64("query_id");
+  auto col_parent_query_id = exporter->RecordUInt64("parent_query_id");
   auto col_cmd_type = exporter->DbOperationColumn();
   auto col_rows = exporter->MetricUInt64("rows");
   auto col_query = exporter->DbQueryTextColumn();
@@ -148,6 +149,7 @@ void ExportEventStats(const std::vector<PschEvent>& events, StatsExporter* expor
     col_username->Append(std::string(ev.username, ev.username_len));
     col_pid->Append(ev.pid);
     col_query_id->Append(static_cast<int64_t>(ev.queryid));
+    col_parent_query_id->Append(static_cast<int64_t>(ev.parent_query_id));
     col_cmd_type->Append(CmdTypeToString(ev.cmd_type));
     col_rows->Append(ev.rows);