Add a check to find tables with zero or one column (#80)

Author: mfvanek

sql/tables_with_zero_or_one_column.sql

@@ -0,0 +1,28 @@
+/*
+ * Copyright (c) 2019-2025. Ivan Vakhrushev and others.
+ * https://github.com/mfvanek/pg-index-health-sql
+ *
+ * Licensed under the Apache License 2.0
+ */
+
+-- Finds tables that have zero or one column.
+-- This usually indicates a poor database design.
+-- If you really need a table with one column, for example, as a global index for partitioned tables,
+-- just ignore the results of this check.
+--
+-- Based on https://github.com/sdblist/db_verifier/blob/main/shards/r1002.sql
+select
+    pc.oid::regclass::text as table_name,
+    pg_table_size(pc.oid) as table_size,
+    coalesce(array_agg(a.attname::text || ',' || a.attnotnull::text order by a.attnum) filter (where a.attname is not null), '{}') as columns
+from
+    pg_catalog.pg_class pc
+    inner join pg_catalog.pg_namespace nsp on nsp.oid = pc.relnamespace
+    left join pg_catalog.pg_attribute a on a.attrelid = pc.oid and a.attnum > 0 and not a.attisdropped
+where
+    pc.relkind in ('r', 'p') and
+    not pc.relispartition and
+    nsp.nspname = :schema_name_param::text
+group by pc.oid
+having count(a.attname) <= 1
+order by table_name;