Check to prevent unnecessary where-clauses in index creating queries on not null columns (#90)

* Standard name for pg_index alias

* Add a check to prevent unnecessary where-clauses in index creating queries on not null columns

Author: mfvanek

CONTRIBUTING.md

@@ -15,11 +15,16 @@ Each database structure check starts with an SQL query to the pg_catalog.
    ```sql
    select
        psui.relid::regclass::text as table_name,
-       psui.indexrelid::regclass::text as index_name,
+       psui.indexrelid::regclass::text as index_name
    ```
 4. All names should be enclosed in double quotes, if required.
-5. All query results must be ordered in some way.
-6. All queries must have a brief description.
+5. The columns for the index or foreign key must be returned in the order they are used in the index or foreign key:
+   ```sql
+   select
+       array_agg(quote_ident(a.attname) || ',' || a.attnotnull::text order by u.ordinality) as columns
+   ```
+6. All query results must be ordered in some way.
+7. All queries must have a brief description.
    Links to documentation or articles with detailed descriptions are welcome.
-7. Name of the sql-file with query must correspond to diagnostic name in [Java project](https://github.com/mfvanek/pg-index-health).
-8. Do not forget to update `README.md`.
+8. Name of the sql-file with query must correspond to diagnostic name in [Java project](https://github.com/mfvanek/pg-index-health).
+9. Do not forget to update `README.md`.

README.md

@@ -52,6 +52,7 @@ For more information please see [PostgreSQL Versioning Policy](https://www.postg
 28. Columns whose names do not follow naming convention ([sql](https://github.com/mfvanek/pg-index-health-sql/blob/master/sql/columns_not_following_naming_convention.sql)).
 29. Primary keys with varchar columns instead of uuids ([sql](https://github.com/mfvanek/pg-index-health-sql/blob/master/sql/primary_keys_with_varchar.sql)).
 30. Columns with [varchar(n)](https://www.postgresql.org/docs/current/datatype-character.html) type ([sql](https://github.com/mfvanek/pg-index-health-sql/blob/master/sql/columns_with_fixed_length_varchar.sql)).
+31. Indexes with unnecessary where-clause on not null column ([sql](https://github.com/mfvanek/pg-index-health-sql/blob/master/sql/indexes_with_unnecessary_where_clause.sql)).
 
 ## Local development
 

sql/btree_indexes_on_array_columns.sql

@@ -11,16 +11,16 @@
 -- Based on query from https://habr.com/ru/articles/800121/
 -- See also https://www.postgresql.org/docs/current/catalog-pg-type.html#CATALOG-TYPCATEGORY-TABLE
 select
-    i.indrelid::regclass::text as table_name,
-    i.indexrelid::regclass::text as index_name,
+    pi.indrelid::regclass::text as table_name,
+    pi.indexrelid::regclass::text as index_name,
     col.attnotnull as column_not_null,
     quote_ident(col.attname) as column_name,
-    pg_relation_size(i.indexrelid) as index_size
-from pg_catalog.pg_index i
-    inner join pg_catalog.pg_class ic on ic.oid = i.indexrelid
+    pg_relation_size(pi.indexrelid) as index_size
+from pg_catalog.pg_index pi
+    inner join pg_catalog.pg_class ic on ic.oid = pi.indexrelid
     inner join pg_catalog.pg_namespace nsp on nsp.oid = ic.relnamespace
     inner join pg_catalog.pg_am am on am.oid = ic.relam and am.amname = 'btree'
-    inner join pg_catalog.pg_attribute col on col.attrelid = i.indrelid and col.attnum = any((string_to_array(i.indkey::text, ' ')::int2[])[:i.indnkeyatts])
+    inner join pg_catalog.pg_attribute col on col.attrelid = pi.indrelid and col.attnum = any((string_to_array(pi.indkey::text, ' ')::int2[])[:pi.indnkeyatts])
     inner join pg_catalog.pg_type typ on typ.oid = col.atttypid
 where
     nsp.nspname = :schema_name_param::text and

sql/columns_with_serial_types.sql

@@ -30,10 +30,10 @@ with
             pg_catalog.pg_class t
             inner join pg_catalog.pg_namespace nsp on nsp.oid = t.relnamespace
             inner join pg_catalog.pg_attribute col on col.attrelid = t.oid
-            inner join pg_attrdef ad on ad.adrelid = col.attrelid and ad.adnum = col.attnum
+            inner join pg_catalog.pg_attrdef ad on ad.adrelid = col.attrelid and ad.adnum = col.attnum
             left join lateral (
                 select sum(case when c.contype = 'p' then +1 else -1 end) as res
-                from pg_constraint c
+                from pg_catalog.pg_constraint c
                 where
                     c.conrelid = col.attrelid and
                     c.conkey[1] = col.attnum and

sql/duplicated_indexes.sql

@@ -11,17 +11,17 @@ select
     string_agg('idx=' || idx::text || ', size=' || pg_relation_size(idx), '; ') as duplicated_indexes
 from (
     select
-        x.indexrelid::regclass as idx,
-        x.indrelid::regclass::text as table_name, /* cast to text for sorting purposes */
+        pi.indexrelid::regclass as idx,
+        pi.indrelid::regclass::text as table_name, /* cast to text for sorting purposes */
         (
-            x.indrelid::text || ' ' || x.indclass::text || ' ' || x.indkey::text || ' ' ||
-            x.indcollation::text || ' ' ||
-            coalesce(pg_get_expr(x.indexprs, x.indrelid), '') || ' ' ||
-            coalesce(pg_get_expr(x.indpred, x.indrelid), '')
+            pi.indrelid::text || ' ' || pi.indclass::text || ' ' || pi.indkey::text || ' ' ||
+            pi.indcollation::text || ' ' ||
+            coalesce(pg_get_expr(pi.indexprs, pi.indrelid), '') || ' ' ||
+            coalesce(pg_get_expr(pi.indpred, pi.indrelid), '')
         ) as grouping_key
     from
-        pg_catalog.pg_index x
-        inner join pg_catalog.pg_class pc on pc.oid = x.indexrelid
+        pg_catalog.pg_index pi
+        inner join pg_catalog.pg_class pc on pc.oid = pi.indexrelid
         inner join pg_catalog.pg_namespace nsp on nsp.oid = pc.relnamespace
     where
         nsp.nspname = :schema_name_param::text and

sql/indexes_with_null_values.sql

@@ -7,21 +7,21 @@
 
 -- Finds indexes that can contain null values.
 select
-    i.indrelid::regclass::text as table_name,
-    i.indexrelid::regclass::text as index_name,
+    pi.indrelid::regclass::text as table_name,
+    pi.indexrelid::regclass::text as index_name,
     string_agg(quote_ident(a.attname), ', ') as nullable_fields, /* in fact, there will always be only one column */
-    pg_relation_size(i.indexrelid) as index_size
+    pg_relation_size(pi.indexrelid) as index_size
 from
-    pg_catalog.pg_index i
-    inner join pg_catalog.pg_class ic on ic.oid = i.indexrelid
+    pg_catalog.pg_index pi
+    inner join pg_catalog.pg_class ic on ic.oid = pi.indexrelid
     inner join pg_catalog.pg_namespace nsp on nsp.oid = ic.relnamespace
-    inner join pg_catalog.pg_attribute a on a.attrelid = i.indrelid and a.attnum = any(i.indkey)
+    inner join pg_catalog.pg_attribute a on a.attrelid = pi.indrelid and a.attnum = any(pi.indkey)
 where
-    not i.indisunique and
+    not pi.indisunique and
     not a.attnotnull and
     not ic.relispartition and
     nsp.nspname = :schema_name_param::text and
-    array_position(i.indkey, a.attnum) = 0 and /* only for first segment */
-    (i.indpred is null or (position(lower(a.attname) in lower(pg_get_expr(i.indpred, i.indrelid))) = 0))
-group by i.indrelid, i.indexrelid, i.indpred
+    array_position(pi.indkey, a.attnum) = 0 and /* only for first segment */
+    (pi.indpred is null or (position(lower(a.attname) in lower(pg_get_expr(pi.indpred, pi.indrelid))) = 0))
+group by pi.indrelid, pi.indexrelid, pi.indpred
 order by table_name, index_name;

sql/indexes_with_unnecessary_where_clause.sql

@@ -0,0 +1,36 @@
+/*
+ * Copyright (c) 2019-2025. Ivan Vakhrushev and others.
+ * https://github.com/mfvanek/pg-index-health-sql
+ *
+ * Licensed under the Apache License 2.0
+ */
+
+-- Finds indexes that have a redundant predicate with the where-clause 'column is not null' for the not null column.
+-- AL01
+select
+    pc.oid::regclass::text as table_name,
+    pi.indexrelid::regclass::text as index_name,
+    pg_relation_size(pi.indexrelid) as index_size,
+    array_agg(quote_ident(a.attname) || ',' || a.attnotnull::text order by u.ordinality) as columns
+from
+    pg_catalog.pg_index pi
+    inner join pg_catalog.pg_class pc on pc.oid = pi.indrelid
+    inner join pg_catalog.pg_namespace nsp on nsp.oid = pc.relnamespace
+    inner join unnest(pi.indkey) with ordinality u(attnum, ordinality) on true
+    inner join pg_catalog.pg_attribute a on a.attrelid = pc.oid and a.attnum = u.attnum
+where
+    pc.relkind in ('r', 'p') and /* regular and partitioned tables */
+    not pc.relispartition and
+    pi.indpred is not null and
+    exists (
+        select 1
+        from
+            unnest(pi.indkey) k(attnum)
+            inner join pg_catalog.pg_attribute att on att.attrelid = pc.oid and att.attnum = k.attnum
+        where
+            att.attnotnull = true and
+            pg_get_indexdef(pi.indexrelid) ilike '%where%' || quote_ident(att.attname) || ' is not null%'
+    ) and
+    nsp.nspname = :schema_name_param::text
+group by pc.oid, pi.indexrelid
+order by table_name, index_name;

sql/invalid_indexes.sql

@@ -8,12 +8,13 @@
 -- Finds invalid indexes that might have appeared as a result of
 -- unsuccessful execution of the 'create index concurrently' command.
 select
-    x.indrelid::regclass::text as table_name,
-    x.indexrelid::regclass::text as index_name
+    pi.indrelid::regclass::text as table_name,
+    pi.indexrelid::regclass::text as index_name,
+    pg_relation_size(pi.indexrelid) as index_size
 from
-    pg_catalog.pg_index x
-    inner join pg_catalog.pg_stat_all_indexes psai on psai.indexrelid = x.indexrelid
+    pg_catalog.pg_index pi
+    inner join pg_catalog.pg_stat_all_indexes psai on psai.indexrelid = pi.indexrelid
 where
     psai.schemaname = :schema_name_param::text and
-    x.indisvalid = false
+    pi.indisvalid = false
 order by table_name, index_name;

sql/primary_keys_with_varchar.sql

@@ -14,32 +14,33 @@
 -- {b9b1f6f5-7f90-4b68-a389-f0ad8bb5784b} - with curly braces - 38 characters
 select
     pc.oid::regclass::text as table_name,
-    i.indexrelid::regclass as index_name,
-    pg_relation_size(i.indexrelid) as index_size,
-    array_agg(quote_ident(a.attname) || ',' || a.attnotnull::text order by a.attnum) as columns
+    pi.indexrelid::regclass as index_name,
+    pg_relation_size(pi.indexrelid) as index_size,
+    array_agg(quote_ident(a.attname) || ',' || a.attnotnull::text order by u.ordinality) as columns
 from
     pg_catalog.pg_class pc
     inner join pg_catalog.pg_namespace nsp on nsp.oid = pc.relnamespace
-    inner join pg_catalog.pg_index i on i.indrelid = pc.oid
-    inner join pg_catalog.pg_attribute a on a.attrelid = pc.oid and a.attnum = any(i.indkey)
+    inner join pg_catalog.pg_index pi on pi.indrelid = pc.oid
+    inner join unnest(pi.indkey) with ordinality u(attnum, ordinality) on true
+    inner join pg_catalog.pg_attribute a on a.attrelid = pc.oid and a.attnum = u.attnum
 where
     not a.attisdropped and
     a.attnum > 0 and
     not pc.relispartition and
     pc.relkind in ('r', 'p') and /* regular and partitioned tables */
-    i.indisprimary and
+    pi.indisprimary and
     exists (
         select 1
         from
             pg_catalog.pg_attribute a2
         where
             a2.attrelid = pc.oid and
-            a2.attnum = any(i.indkey) and
+            a2.attnum = any(pi.indkey) and
             not a2.attisdropped and
             a2.attnum > 0 and
             a2.atttypid = any('{varchar,bpchar}'::regtype[]) and
             (a2.atttypmod - 4) in (32, 36, 38)
     ) and
     nsp.nspname = :schema_name_param::text
-group by pc.oid, i.indexrelid
+group by pc.oid, pi.indexrelid
 order by table_name, index_name;

sql/unused_indexes.sql

@@ -20,26 +20,26 @@ with
     ),
 
     foreign_key_indexes as (
-        select i.indexrelid
+        select pi.indexrelid
         from
             pg_catalog.pg_constraint c
             inner join nsp on nsp.oid = c.connamespace
             inner join lateral unnest(c.conkey) with ordinality u(attnum, attposition) on true
-            inner join pg_catalog.pg_index i on i.indrelid = c.conrelid and (c.conkey::int[] <@ i.indkey::int[])
+            inner join pg_catalog.pg_index pi on pi.indrelid = c.conrelid and (c.conkey::int[] <@ pi.indkey::int[])
         where c.contype = 'f'
     )
 
 select
     psui.relid::regclass::text as table_name,
     psui.indexrelid::regclass::text as index_name,
     psui.idx_scan as index_scans,
-    pg_relation_size(i.indexrelid) as index_size
+    pg_relation_size(pi.indexrelid) as index_size
 from
     pg_catalog.pg_stat_user_indexes psui
-    inner join pg_catalog.pg_index i on i.indexrelid = psui.indexrelid
+    inner join pg_catalog.pg_index pi on pi.indexrelid = psui.indexrelid
 where
     psui.schemaname in (select nspname from nsp) and
-    not i.indisunique and
-    i.indexrelid not in (select * from foreign_key_indexes) and /* retain indexes on foreign keys */
+    not pi.indisunique and
+    pi.indexrelid not in (select * from foreign_key_indexes) and /* retain indexes on foreign keys */
     psui.idx_scan < 50::integer
-order by table_name, pg_relation_size(i.indexrelid) desc;
+order by table_name, pg_relation_size(pi.indexrelid) desc;