Issue 380: ALTER TABLE ADD FOREIGN KEY with an explicit index didn't verify the…

Issue 380: ALTER TABLE ADD FOREIGN KEY with an explicit index didn't verify the index can be used, which would lead to a NullPointerException later on.

h2/src/docsrc/html/changelog.html

@@ -18,7 +18,9 @@ Change Log
 <h1>Change Log</h1>
 
 <h2>Next Version (unreleased)</h2>
-<ul><li>The wrong kind of exception (NullPointerException) was thrown in a UNION query
+<ul><li>Issue 380: ALTER TABLE ADD FOREIGN KEY with an explicit index didn't verify
+    the index can be used, which would lead to a NullPointerException later on.
+</li><li>The wrong kind of exception (NullPointerException) was thrown in a UNION query
     with an incorrect ORDER BY expression.
 </li><li>Issue 362: support LIMIT in UPDATE statements.
 </li><li>Browser: if no default browser is set, Google Chrome is now used if available.

h2/src/main/org/h2/command/ddl/AlterTableAddConstraint.java

@@ -199,7 +199,8 @@ public class AlterTableAddConstraint extends SchemaCommand {
                 throw DbException.get(ErrorCode.COLUMN_COUNT_DOES_NOT_MATCH);
             }
             boolean isRefOwner = false;
-            if (refIndex != null && refIndex.getTable() == refTable) {
+            if (refIndex != null && refIndex.getTable() == refTable &&
+                    canUseIndex(refIndex, refTable, refIndexColumns)) {
                 isRefOwner = true;
                 refIndex.getIndexType().setBelongsToConstraint(true);
             } else {

h2/src/main/org/h2/res/help.csv

@@ -22,7 +22,7 @@ Inserts a new row / new rows into a table."
 "Commands (DML)","UPDATE","
 UPDATE tableName [ [ AS ] newTableAlias ]
 SET { columnName = { DEFAULT | expression } } [,...]
-[ WHERE expression ]
+[ WHERE expression ] [ LIMIT expression ]
 ","
 Updates data in a table."
 "Commands (DML)","DELETE","

h2/src/test/org/h2/test/test-1.3.txt

 --- special grammar and test cases ---------------------------------------------------------------------------------------------
+create table test (id int not null, pid int);
+> ok
+
+create index idx_test_pid on test (pid);
+> ok
+
+alter table test add constraint fk_test foreign key (pid) 
+references test (id) index idx_test_pid;
+> ok
+
+insert into test values (2, null);
+> ok
+
+update test set pid = 1 where id = 2;
+> ok
+
+drop table test;
+> ok
+
 call cast('null' as uuid);
 > exception