Fix c77_dbh_get_mv_details to handle stats_reset outside aggregation

health_functions.sql

@@ -38,11 +38,39 @@ $$ LANGUAGE plpgsql;
 CREATE OR REPLACE FUNCTION public.c77_dbh_get_mv_details(p_mv_name text)
     RETURNS JSON AS $$
 DECLARE
-    v_io_load numeric;  -- Estimated I/O rate (blocks/sec)
+    v_io_load numeric;      -- Blocks read per second
-    v_cpu_wait boolean; -- True if waiting on CPU
+    v_cpu_time numeric;     -- CPU time per call (ms)
-    v_mem_pressure numeric; -- Buffer hit ratio (lower = more memory pressure)
+    v_mem_hit_ratio numeric; -- Cache hit ratio
+    v_has_pg_stat_statements boolean; -- Check if extension is available
+    v_stats_reset timestamp; -- Time of last stats reset
 BEGIN
-    -- Calculate system stats
+    -- Check if pg_stat_statements is installed
+    SELECT EXISTS (
+        SELECT 1 FROM pg_extension WHERE extname = 'pg_stat_statements'
+    ) INTO v_has_pg_stat_statements;
+
+    -- Get stats_reset separately for the current database
+    SELECT stats_reset
+    INTO v_stats_reset
+    FROM pg_stat_database
+    WHERE datname = current_database();
+
+    -- If pg_stat_statements is available, use it for refined stats
+    IF v_has_pg_stat_statements THEN
+        SELECT
+            COALESCE(SUM(s.shared_blks_read) / EXTRACT(EPOCH FROM (NOW() - v_stats_reset)), 0) AS io_load,
+            COALESCE(SUM(s.total_time) / GREATEST(SUM(s.calls), 1), 0) AS cpu_time,
+            CASE
+                WHEN SUM(s.shared_blks_hit + s.shared_blks_read) = 0 THEN 1.0
+                ELSE SUM(s.shared_blks_hit)::numeric / (SUM(s.shared_blks_hit) + SUM(s.shared_blks_read))
+                END AS mem_hit_ratio
+        INTO v_io_load, v_cpu_time, v_mem_hit_ratio
+        FROM pg_stat_statements s
+                 JOIN pg_stat_database d ON s.dbid = d.datid
+        WHERE s.query ILIKE '%REFRESH MATERIALIZED VIEW ' || p_mv_name || '%'
+          AND d.datname = current_database();
+    ELSE
+        -- Fallback to basic stats without pg_stat_statements
         SELECT
             (d.blks_read + d.blks_hit) / EXTRACT(EPOCH FROM (NOW() - d.stats_reset)) AS io_load,
             EXISTS (
@@ -51,15 +79,16 @@ BEGIN
                 WHERE query ILIKE '%REFRESH MATERIALIZED VIEW%'
                   AND wait_event_type = 'CPU'
                   AND state = 'active'
-        ) AS cpu_wait,
+            )::numeric AS cpu_time, -- 1 if waiting, 0 if not (crude proxy)
             CASE
                 WHEN b.buffers_clean + b.buffers_backend = 0 THEN 1.0
                 ELSE b.buffers_clean::numeric / (b.buffers_clean + b.buffers_backend)
-            END AS mem_pressure
+                END AS mem_hit_ratio
-    INTO v_io_load, v_cpu_wait, v_mem_pressure
+        INTO v_io_load, v_cpu_time, v_mem_hit_ratio
         FROM pg_stat_database d
                  CROSS JOIN pg_stat_bgwriter b
         WHERE d.datname = current_database();
+    END IF;
 
     RETURN (
         SELECT json_build_object(
@@ -76,15 +105,15 @@ BEGIN
                                        ELSE 1
                            END,
                        'insight', CASE
-                                      WHEN v_io_load > 1000 THEN 'Refreshes are slower due to high I/O load.'
+                                      WHEN v_io_load > 100 THEN 'Refreshes are slower due to high I/O load.'
-                                      WHEN v_cpu_wait THEN 'Refreshes are slower due to CPU contention.'
+                                      WHEN v_cpu_time > (CASE WHEN v_has_pg_stat_statements THEN 1000 ELSE 0.5 END) THEN 'Refreshes are slower due to CPU usage.'
-                                      WHEN v_mem_pressure < 0.9 THEN 'Refreshes are slower due to memory pressure.'
+                                      WHEN v_mem_hit_ratio < 0.9 THEN 'Refreshes are slower due to memory pressure.'
                                       ELSE 'Refreshes are performing normally.'
                            END,
                        'action', CASE
-                                     WHEN v_io_load > 1000 THEN 'Optimize I/O or schedule during off-peak hours.'
+                                     WHEN v_io_load > 100 THEN 'Optimize I/O or schedule during off-peak hours.'
-                                     WHEN v_cpu_wait THEN 'Increase CPU capacity or reduce concurrent load.'
+                                     WHEN v_cpu_time > (CASE WHEN v_has_pg_stat_statements THEN 1000 ELSE 0.5 END) THEN 'Increase CPU capacity or optimize queries.'
-                                     WHEN v_mem_pressure < 0.9 THEN 'Adjust memory settings (e.g., shared_buffers).'
+                                     WHEN v_mem_hit_ratio < 0.9 THEN 'Adjust memory settings (e.g., work_mem, shared_buffers).'
                                      ELSE 'No action needed.'
                            END,
                        'details', json_build_object(
@@ -94,19 +123,25 @@ BEGIN
                                'max_refresh_time', refresh_mv_time_max::text,
                                'refresh_count', refresh_count,
                                'io_load', round(v_io_load)::text || ' blocks/sec',
-                               'cpu_waiting', v_cpu_wait::text,
+                               'cpu_time', (CASE
-                               'buffer_hit_ratio', round(v_mem_pressure * 100)::text || '%',
+                                                WHEN v_has_pg_stat_statements THEN round(v_cpu_time)::text || ' ms/call'
+                                                ELSE (v_cpu_time * 100)::text || '% waiting'
+                            END),
+                               'buffer_hit_ratio', round(v_mem_hit_ratio * 100)::text || '%',
                                'bottleneck', CASE
-                                                 WHEN v_io_load > 1000 THEN 'I/O'
+                                                 WHEN v_io_load > 100 THEN 'I/O'
-                                                 WHEN v_cpu_wait THEN 'CPU'
+                                                 WHEN v_cpu_time > (CASE WHEN v_has_pg_stat_statements THEN 1000 ELSE 0.5 END) THEN 'CPU'
-                                                 WHEN v_mem_pressure < 0.9 THEN 'RAM'
+                                                 WHEN v_mem_hit_ratio < 0.9 THEN 'RAM'
                                                  ELSE 'None'
                                    END,
                                'explanations', json_build_object(
                                        'last_refresh_time', 'Last refresh duration compared to historical min/max.',
-                                       'io_load', 'High I/O load (blocks/sec) indicates disk operations are limiting performance.',
+                                       'io_load', 'Blocks read per second; high values indicate disk I/O bottleneck.',
-                                       'cpu_waiting', 'True if the refresh is waiting on CPU resources.',
+                                       'cpu_time', (CASE
-                                       'buffer_hit_ratio', 'Lower ratio means more disk access due to memory pressure.'
+                                                        WHEN v_has_pg_stat_statements THEN 'Average CPU time per refresh; high values suggest CPU bottleneck.'
+                                                        ELSE 'Percentage of time waiting on CPU (crude estimate).'
+                                    END),
+                                       'buffer_hit_ratio', 'Percentage of blocks from cache; <90% suggests memory pressure.'
                                                )
                                   )
                )