HHH-16252 SQL syntax error on drop constraint

hibernate-core/src/main/java/org/hibernate/dialect/unique/AlterTableUniqueDelegate.java

@@ -76,14 +76,21 @@ public class AlterTableUniqueDelegate implements UniqueDelegate {
 			SqlStringGenerationContext context) {
 		final String tableName = context.format( uniqueKey.getTable().getQualifiedTableName() );
 		final StringBuilder command = new StringBuilder( dialect.getAlterTableString(tableName) );
+		command.append( ' ' );
 		command.append( dialect.getDropUniqueKeyString() );
 		if ( dialect.supportsIfExistsBeforeConstraintName() ) {
-			command.append( "if exists " );
+			command.append( " if exists " );
+			command.append( dialect.quote( uniqueKey.getName() ) );
 		}
-		command.append( dialect.quote( uniqueKey.getName() ) );
-		if ( dialect.supportsIfExistsAfterConstraintName() ) {
+		else if ( dialect.supportsIfExistsAfterConstraintName() ) {
+			command.append( ' ' );
+			command.append( dialect.quote( uniqueKey.getName() ) );
 			command.append( " if exists" );
 		}
+		else {
+			command.append( ' ' );
+			command.append( dialect.quote( uniqueKey.getName() ) );
+		}
 		return command.toString();
 	}
 

hibernate-core/src/test/java/org/hibernate/orm/test/dialect/PostgreSQLDialectTestCase.java

@@ -14,10 +14,20 @@ import org.hibernate.JDBCException;
 import org.hibernate.LockMode;
 import org.hibernate.LockOptions;
 import org.hibernate.PessimisticLockException;
+import org.hibernate.boot.model.naming.Identifier;
+import org.hibernate.boot.model.relational.QualifiedName;
+import org.hibernate.boot.model.relational.QualifiedSequenceName;
+import org.hibernate.boot.model.relational.QualifiedTableName;
+import org.hibernate.boot.model.relational.SqlStringGenerationContext;
+import org.hibernate.dialect.Dialect;
 import org.hibernate.dialect.PostgreSQLDialect;
 import org.hibernate.QueryTimeoutException;
+import org.hibernate.dialect.unique.AlterTableUniqueDelegate;
+import org.hibernate.engine.jdbc.env.spi.IdentifierHelper;
 import org.hibernate.exception.LockAcquisitionException;
 import org.hibernate.exception.spi.SQLExceptionConversionDelegate;
+import org.hibernate.mapping.Table;
+import org.hibernate.mapping.UniqueKey;
 
 import org.hibernate.testing.TestForIssue;
 import org.hibernate.testing.junit4.BaseUnitTestCase;
@@ -124,4 +134,86 @@ public class PostgreSQLDialectTestCase extends BaseUnitTestCase {
 
 		assertEquals("alter table if exists table_name", dialect.getAlterTableString( "table_name" ));
 	}
+
+	@Test
+	@TestForIssue( jiraKey = "HHH-16252" )
+	public void testAlterTableDropConstraintString() {
+		PostgreSQLDialect dialect = new PostgreSQLDialect();
+		AlterTableUniqueDelegate alterTable = new AlterTableUniqueDelegate( dialect );
+		final Table table = new Table( "orm", "table_name" );
+		final UniqueKey uniqueKey = new UniqueKey();
+		uniqueKey.setName( "unique_something" );
+		uniqueKey.setTable( table );
+		final String sql = alterTable.getAlterTableToDropUniqueKeyCommand(
+				uniqueKey,
+				null,
+				new MockSqlStringGenerationContext()
+		);
+
+		assertEquals("alter table if exists table_name drop constraint if exists unique_something", sql );
+	}
+
+	private static class MockSqlStringGenerationContext implements SqlStringGenerationContext {
+
+		@Override
+		public Dialect getDialect() {
+			return null;
+		}
+
+		@Override
+		public IdentifierHelper getIdentifierHelper() {
+			return null;
+		}
+
+		@Override
+		public Identifier toIdentifier(String text) {
+			return null;
+		}
+
+		@Override
+		public Identifier getDefaultCatalog() {
+			return null;
+		}
+
+		@Override
+		public Identifier catalogWithDefault(Identifier explicitCatalogOrNull) {
+			return null;
+		}
+
+		@Override
+		public Identifier getDefaultSchema() {
+			return null;
+		}
+
+		@Override
+		public Identifier schemaWithDefault(Identifier explicitSchemaOrNull) {
+			return null;
+		}
+
+		@Override
+		public String format(QualifiedTableName qualifiedName) {
+			return qualifiedName.getTableName().render();
+		}
+
+		@Override
+		public String format(QualifiedSequenceName qualifiedName) {
+			return null;
+		}
+
+		@Override
+		public String format(QualifiedName qualifiedName) {
+			return null;
+		}
+
+		@Override
+		public String formatWithoutCatalog(QualifiedSequenceName qualifiedName) {
+			return null;
+		}
+
+		@Override
+		public boolean isMigration() {
+			return false;
+		}
+	}
+
 }

hibernate-core/src/test/java/org/hibernate/orm/test/schemaupdate/inheritance/tableperclass/SchemaCreationTest.java

@@ -88,9 +88,9 @@ public class SchemaCreationTest {
 						&& statement.contains("category (code)")
 					|| statement.startsWith("create unique nonclustered index")
 					&& statement.contains("category (code)")
-					|| statement.startsWith("alter table if exists category add constraint")
+					|| statement.startsWith("alter table if exists category add constraint ")
 						&& statement.contains("unique (code)")
-					|| statement.startsWith("alter table category add constraint")
+					|| statement.startsWith("alter table category add constraint ")
 						&& statement.contains("unique (code)")
 					|| statement.startsWith("create table category")
 						&& statement.contains("code " + varchar255 + " not null unique")

hibernate-core/src/test/java/org/hibernate/orm/test/schemaupdate/uniqueconstraint/UniqueConstraintDropTest.java

@@ -139,11 +139,11 @@ public class UniqueConstraintDropTest {
 	}
 
 	private boolean checkDropConstraint(String tableName, String columnName) throws IOException {
-		String regex = getDialect().getAlterTableString( tableName ) + getDialect().getDropUniqueKeyString();
+		String regex = getDialect().getAlterTableString( tableName ) + ' ' + getDialect().getDropUniqueKeyString();
 		if ( getDialect().supportsIfExistsBeforeConstraintName() ) {
-			regex += "if exists ";
+			regex += " if exists";
 		}
-		regex += "uk_.*";
+		regex += " uk_.*";
 		if ( getDialect().supportsIfExistsAfterConstraintName() ) {
 			regex += " if exists";
 		}