Block ALTER TABLE .. DROP NOT NULL on columns in replica identity index

Replica identities that depend directly on an index rely on a set of
properties, one of them being that all the columns defined in this index
have to be marked as NOT NULL.  There was a hole in the logic with ALTER
TABLE DROP NOT NULL, where it was possible to remove the NOT NULL
property of a column part of an index used as replica identity, so block
it to avoid problems with logical decoding down the road.

The same check was already done columns part of a primary key, so the
fix is straight-forward.

Author: Haiying Tang, Hou Zhijie
Reviewed-by: Dilip Kumar, Michael Paquier
Discussion: https://postgr.es/m/OS0PR01MB6113338C102BEE8B2FFC5BD9FB619@OS0PR01MB6113.jpnprd01.prod.outlook.com
Backpatch-through: 10

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 6dacda0634e1de12ec0c012b5af8ab8f7282093f..b9ea5280efae966ceff44053b26793a5d0e1a47a 100644 (file)
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -7020,7 +7020,8 @@ ATExecDropNotNull(Relation rel, const char *colName, LOCKMODE lockmode)
                        colName, RelationGetRelationName(rel))));
 
    /*
-    * Check that the attribute is not in a primary key
+    * Check that the attribute is not in a primary key or in an index used as
+    * a replica identity.
     *
     * Note: we'll throw error even if the pkey index is not valid.
     */
@@ -7040,20 +7041,32 @@ ATExecDropNotNull(Relation rel, const char *colName, LOCKMODE lockmode)
            elog(ERROR, "cache lookup failed for index %u", indexoid);
        indexStruct = (Form_pg_index) GETSTRUCT(indexTuple);
 
-       /* If the index is not a primary key, skip the check */
-       if (indexStruct->indisprimary)
+       /*
+        * If the index is not a primary key or an index used as replica
+        * identity, skip the check.
+        */
+       if (indexStruct->indisprimary || indexStruct->indisreplident)
        {
            /*
-            * Loop over each attribute in the primary key and see if it
-            * matches the to-be-altered attribute
+            * Loop over each attribute in the primary key or the index used
+            * as replica identity and see if it matches the to-be-altered
+            * attribute.
             */
            for (i = 0; i < indexStruct->indnkeyatts; i++)
            {
                if (indexStruct->indkey.values[i] == attnum)
-                   ereport(ERROR,
-                           (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
-                            errmsg("column \"%s\" is in a primary key",
-                                   colName)));
+               {
+                   if (indexStruct->indisprimary)
+                       ereport(ERROR,
+                               (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
+                                errmsg("column \"%s\" is in a primary key",
+                                       colName)));
+                   else
+                       ereport(ERROR,
+                               (errcode(ERRCODE_INVALID_TABLE_DEFINITION),
+                                errmsg("column \"%s\" is in index used as replica identity",
+                                       colName)));
+               }
            }
        }
 

diff --git a/src/test/regress/expected/replica_identity.out b/src/test/regress/expected/replica_identity.out
index 79002197a7af688a117d8f15fa0b4e9e277b577e..e25ec06a842429432a61706077b203e89f60f586 100644 (file)
--- a/src/test/regress/expected/replica_identity.out
+++ b/src/test/regress/expected/replica_identity.out
@@ -223,6 +223,10 @@ ALTER TABLE test_replica_identity3 ALTER COLUMN id TYPE bigint;
 Indexes:
     "test_replica_identity3_id_key" UNIQUE, btree (id) REPLICA IDENTITY
 
+-- ALTER TABLE DROP NOT NULL is not allowed for columns part of an index
+-- used as replica identity.
+ALTER TABLE test_replica_identity3 ALTER COLUMN id DROP NOT NULL;
+ERROR:  column "id" is in index used as replica identity
 DROP TABLE test_replica_identity;
 DROP TABLE test_replica_identity2;
 DROP TABLE test_replica_identity3;

diff --git a/src/test/regress/sql/replica_identity.sql b/src/test/regress/sql/replica_identity.sql
index a5ac8f55673abd5fb716eae05275f1cc52edfa4c..33da8297132e9efc435c5b56794668a6ebcab6b2 100644 (file)
--- a/src/test/regress/sql/replica_identity.sql
+++ b/src/test/regress/sql/replica_identity.sql
@@ -94,6 +94,10 @@ ALTER TABLE test_replica_identity3 REPLICA IDENTITY USING INDEX test_replica_ide
 ALTER TABLE test_replica_identity3 ALTER COLUMN id TYPE bigint;
 \d test_replica_identity3
 
+-- ALTER TABLE DROP NOT NULL is not allowed for columns part of an index
+-- used as replica identity.
+ALTER TABLE test_replica_identity3 ALTER COLUMN id DROP NOT NULL;
+
 DROP TABLE test_replica_identity;
 DROP TABLE test_replica_identity2;
 DROP TABLE test_replica_identity3;