Fix pg_stat_kcache support when not all metrics are available.

The plan_* fields can be NULL if pg_stat_kcache.track_planning isn't enable.
Most of the exec_* fields can also be NULL on system without getrusage()
support.

powa--4.1.4--4.2.0.sql

@@ -309,3 +309,26 @@ BEGIN
     DELETE FROM powa_statements_history_current_db WHERE srvid = _srvid;
 END;
 $PROC$ LANGUAGE plpgsql; /* end of powa_statements_aggregate */
+
+ALTER TABLE public.powa_kcache_src_tmp ALTER COLUMN plan_reads DROP NOT NULL;
+ALTER TABLE public.powa_kcache_src_tmp ALTER COLUMN plan_writes DROP NOT NULL;
+ALTER TABLE public.powa_kcache_src_tmp ALTER COLUMN plan_user_time DROP NOT NULL;
+ALTER TABLE public.powa_kcache_src_tmp ALTER COLUMN plan_system_time DROP NOT NULL;
+ALTER TABLE public.powa_kcache_src_tmp ALTER COLUMN plan_minflts DROP NOT NULL;
+ALTER TABLE public.powa_kcache_src_tmp ALTER COLUMN plan_majflts DROP NOT NULL;
+ALTER TABLE public.powa_kcache_src_tmp ALTER COLUMN plan_nswaps DROP NOT NULL;
+ALTER TABLE public.powa_kcache_src_tmp ALTER COLUMN plan_msgsnds DROP NOT NULL;
+ALTER TABLE public.powa_kcache_src_tmp ALTER COLUMN plan_msgrcvs DROP NOT NULL;
+ALTER TABLE public.powa_kcache_src_tmp ALTER COLUMN plan_nsignals DROP NOT NULL;
+ALTER TABLE public.powa_kcache_src_tmp ALTER COLUMN plan_nvcsws DROP NOT NULL;
+ALTER TABLE public.powa_kcache_src_tmp ALTER COLUMN plan_nivcsws DROP NOT NULL;
+ALTER TABLE public.powa_kcache_src_tmp ALTER COLUMN exec_reads DROP NOT NULL;
+ALTER TABLE public.powa_kcache_src_tmp ALTER COLUMN exec_writes DROP NOT NULL;
+ALTER TABLE public.powa_kcache_src_tmp ALTER COLUMN exec_minflts DROP NOT NULL;
+ALTER TABLE public.powa_kcache_src_tmp ALTER COLUMN exec_majflts DROP NOT NULL;
+ALTER TABLE public.powa_kcache_src_tmp ALTER COLUMN exec_nswaps DROP NOT NULL;
+ALTER TABLE public.powa_kcache_src_tmp ALTER COLUMN exec_msgsnds DROP NOT NULL;
+ALTER TABLE public.powa_kcache_src_tmp ALTER COLUMN exec_msgrcvs DROP NOT NULL;
+ALTER TABLE public.powa_kcache_src_tmp ALTER COLUMN exec_nsignals DROP NOT NULL;
+ALTER TABLE public.powa_kcache_src_tmp ALTER COLUMN exec_nvcsws DROP NOT NULL;
+ALTER TABLE public.powa_kcache_src_tmp ALTER COLUMN exec_nivcsws DROP NOT NULL;

powa--4.2.0.sql

@@ -1385,30 +1385,30 @@ CREATE UNLOGGED TABLE public.powa_kcache_src_tmp(
     top              bool NOT NULL,
     userid           oid NOT NULL,
     dbid             oid NOT NULL,
-    plan_reads       bigint NOT NULL,
-    plan_writes      bigint NOT NULL,
-    plan_user_time   double precision NOT NULL,
-    plan_system_time double precision NOT NULL,
-    plan_minflts     bigint NOT NULL,
-    plan_majflts     bigint NOT NULL,
-    plan_nswaps      bigint NOT NULL,
-    plan_msgsnds     bigint NOT NULL,
-    plan_msgrcvs     bigint NOT NULL,
-    plan_nsignals    bigint NOT NULL,
-    plan_nvcsws      bigint NOT NULL,
-    plan_nivcsws     bigint NOT NULL,
-    exec_reads       bigint NOT NULL,
-    exec_writes      bigint NOT NULL,
+    plan_reads       bigint,
+    plan_writes      bigint,
+    plan_user_time   double precision,
+    plan_system_time double precision,
+    plan_minflts     bigint,
+    plan_majflts     bigint,
+    plan_nswaps      bigint,
+    plan_msgsnds     bigint,
+    plan_msgrcvs     bigint,
+    plan_nsignals    bigint,
+    plan_nvcsws      bigint,
+    plan_nivcsws     bigint,
+    exec_reads       bigint,
+    exec_writes      bigint,
     exec_user_time   double precision NOT NULL,
     exec_system_time double precision NOT NULL,
-    exec_minflts     bigint NOT NULL,
-    exec_majflts     bigint NOT NULL,
-    exec_nswaps      bigint NOT NULL,
-    exec_msgsnds     bigint NOT NULL,
-    exec_msgrcvs     bigint NOT NULL,
-    exec_nsignals    bigint NOT NULL,
-    exec_nvcsws      bigint NOT NULL,
-    exec_nivcsws     bigint NOT NULL
+    exec_minflts     bigint,
+    exec_majflts     bigint,
+    exec_nswaps      bigint,
+    exec_msgsnds     bigint,
+    exec_msgrcvs     bigint,
+    exec_nsignals    bigint,
+    exec_nvcsws      bigint,
+    exec_nivcsws     bigint
 );
 
 CREATE TYPE public.powa_kcache_type AS (