Referenced objects in check constraints could be dropped, which resulted in a…

Referenced objects in check constraints could be dropped, which resulted in a database that can't be opened normally.

h2/src/main/org/h2/constraint/Constraint.java

@@ -9,6 +9,7 @@ package org.h2.constraint;
 import java.util.HashSet;
 import org.h2.engine.DbObject;
 import org.h2.engine.Session;
+import org.h2.expression.ExpressionVisitor;
 import org.h2.index.Index;
 import org.h2.message.DbException;
 import org.h2.message.Trace;
@@ -179,4 +180,15 @@ public abstract class Constraint extends SchemaObjectBase implements Comparable<
         return table.isHidden();
     }
 
+    /**
+     * Visit all elements in the constraint.
+     *
+     * @param visitor the visitor
+     * @return true if every visited expression returned true, or if there are
+     *         no expressions
+     */
+    public boolean isEverything(ExpressionVisitor visitor) {
+        return true;
+    }
+
 }

h2/src/main/org/h2/constraint/ConstraintCheck.java

@@ -140,4 +140,8 @@ public class ConstraintCheck extends Constraint {
         // nothing to do
     }
 
+    public boolean isEverything(ExpressionVisitor visitor) {
+        return expr.isEverything(visitor);
+    }
+
 }

h2/src/main/org/h2/table/Table.java

@@ -311,6 +311,10 @@ public abstract class Table extends SchemaObjectBase {
      * @param dependencies the current set of dependencies
      */
     public void addDependencies(HashSet<DbObject> dependencies) {
+        if (dependencies.contains(this)) {
+            // avoid endless recursion
+            return;
+        }
         if (sequences != null) {
             for (Sequence s : sequences) {
                 dependencies.add(s);
@@ -320,6 +324,12 @@ public abstract class Table extends SchemaObjectBase {
         for (Column col : columns) {
             col.isEverything(visitor);
         }
+        if (constraints != null) {
+            for (Constraint c : constraints) {
+                c.isEverything(visitor);
+            }
+        }
+        dependencies.add(this);
     }
 
     public ArrayList<DbObject> getChildren() {

h2/src/test/org/h2/test/db/TestCases.java

@@ -37,6 +37,7 @@ public class TestCases extends TestBase {
     }
 
     public void test() throws Exception {
+        testDependencies();
         testConvertType();
         testSortedSelect();
         testMaxMemoryRowsDistinct();
@@ -92,6 +93,43 @@ public class TestCases extends TestBase {
         deleteDb("cases");
     }
 
+    private void testDependencies() throws SQLException {
+        deleteDb("cases");
+        Connection conn = getConnection("cases");
+        Statement stat = conn.createStatement();
+
+        // avoid endless recursion when adding dependencies
+        stat.execute("create table test(id int primary key, parent int)");
+        stat.execute("alter table test add constraint test check (select count(*) from test) < 10");
+        stat.execute("create table b()");
+        stat.execute("drop table b");
+        stat.execute("drop table test");
+
+        // ensure the dependency is detected
+        stat.execute("create alias is_positive as 'boolean isPositive(int x) { return x > 0; }'");
+        stat.execute("create table a(a integer, constraint test check is_positive(a))");
+        try {
+            stat.execute("drop alias is_positive");
+            fail();
+        } catch (SQLException e) {
+            assertEquals(ErrorCode.CANNOT_DROP_2, e.getErrorCode());
+        }
+        stat.execute("drop table a");
+        stat.execute("drop alias is_positive");
+
+        // ensure trying to reference the table fails
+        // (otherwise re-opening the database is not possible)
+        stat.execute("create table test(id int primary key)");
+        try {
+            stat.execute("alter table test alter column id set default ifnull((select max(id) from test for update)+1, 0)");
+            fail();
+        } catch (SQLException e) {
+            assertEquals(ErrorCode.COLUMN_IS_REFERENCED_1, e.getErrorCode());
+        }
+        stat.execute("drop table test");
+        conn.close();
+    }
+
     private void testConvertType() throws SQLException {
         deleteDb("cases");
         Connection conn = getConnection("cases");
@@ -101,6 +139,7 @@ public class TestCases extends TestBase {
         assertEquals(2, meta.getPrecision(1));
         assertEquals(2, meta.getScale(1));
         stat.execute("alter table test add column y int");
+        stat.execute("drop table test");
         conn.close();
     }