HHH-11647 - Use ALTER TABLE IF EXISTS on Postgres

hibernate-core/src/main/java/org/hibernate/dialect/Dialect.java

@@ -1451,6 +1451,22 @@ public abstract class Dialect implements ConversionContext {
 		return "create table";
 	}
 
+	/**
+	 * Command used to alter a table.
+	 *
+	 * @param tableName The name of the table to alter
+	 * @return The command used to alter a table.
+	 * @since 5.2.11
+	 */
+	public String getAlterTableString(String tableName) {
+		final StringBuilder sb = new StringBuilder( "alter table " );
+		if ( supportsIfExistsAfterAlterTable() ) {
+			sb.append( "if exists " );
+		}
+		sb.append( tableName );
+		return sb.toString();
+	}
+
 	/**
 	 * Slight variation on {@link #getCreateTableString}.  Here, we have the
 	 * command used to create a table when there is no primary key and
@@ -2241,6 +2257,16 @@ public abstract class Dialect implements ConversionContext {
 		return false;
 	}
 
+	/**
+	 * For an "alter table", can the phrase "if exists" be applied?
+	 *
+	 * @return {@code true} if the "if exists" can be applied after ALTER TABLE
+	 * @since 5.2.11
+	 */
+	public boolean supportsIfExistsAfterAlterTable() {
+		return false;
+	}
+
 	/**
 	 * Generate a DROP TABLE statement
 	 *

hibernate-core/src/main/java/org/hibernate/dialect/PostgreSQL92Dialect.java

@@ -22,4 +22,10 @@ public class PostgreSQL92Dialect extends PostgreSQL91Dialect {
 		super();
 		this.registerColumnType( Types.JAVA_OBJECT, "json" );
 	}
+
+	@Override
+	public boolean supportsIfExistsAfterAlterTable() {
+		return true;
+	}
+
 }

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

@@ -53,7 +53,8 @@ public class DefaultUniqueDelegate implements UniqueDelegate {
 		);
 
 		final String constraintName = dialect.quote( uniqueKey.getName() );
-		return "alter table " + tableName + " add constraint " + constraintName + " " + uniqueConstraintSql( uniqueKey );
+		return dialect.getAlterTableString( tableName )
+				+ " add constraint " + constraintName + " " + uniqueConstraintSql( uniqueKey );
 	}
 
 	protected String uniqueConstraintSql(UniqueKey uniqueKey) {
@@ -83,8 +84,7 @@ public class DefaultUniqueDelegate implements UniqueDelegate {
 				dialect
 		);
 
-		final StringBuilder buf = new StringBuilder( "alter table " );
+		final StringBuilder buf = new StringBuilder( dialect.getAlterTableString(tableName) );
-		buf.append( tableName );
 		buf.append( getDropUnique() );
 		if ( dialect.supportsIfExistsBeforeConstraintName() ) {
 			buf.append( "if exists " );

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

@@ -32,7 +32,8 @@ public class InformixUniqueDelegate extends DefaultUniqueDelegate {
 				metadata.getDatabase().getJdbcEnvironment().getDialect()
 		);
 		final String constraintName = dialect.quote( uniqueKey.getName() );
-		return "alter table " + tableName + " add constraint " + uniqueConstraintSql( uniqueKey ) + " constraint " + constraintName;
+		return dialect.getAlterTableString( tableName )
+				+ " add constraint " + uniqueConstraintSql( uniqueKey ) + " constraint " + constraintName;
 	}
 
 }

hibernate-core/src/main/java/org/hibernate/mapping/Constraint.java

@@ -165,10 +165,11 @@ public abstract class Constraint implements RelationalModel, Exportable, Seriali
 
 	public String sqlDropString(Dialect dialect, String defaultCatalog, String defaultSchema) {
 		if ( isGenerated( dialect ) ) {
+			final String tableName = getTable().getQualifiedName( dialect, defaultCatalog, defaultSchema );
 			return String.format(
 					Locale.ROOT,
-					"alter table %s drop constraint %s",
+					"%s drop constraint %s",
-					getTable().getQualifiedName( dialect, defaultCatalog, defaultSchema ),
+					dialect.getAlterTableString( tableName ),
 					dialect.quote( getName() )
 			);
 		}
@@ -184,8 +185,8 @@ public abstract class Constraint implements RelationalModel, Exportable, Seriali
 			// empty string.  Prevent blank "alter table" statements.
 			String constraintString = sqlConstraintString( dialect, getName(), defaultCatalog, defaultSchema );
 			if ( !StringHelper.isEmpty( constraintString ) ) {
-				return "alter table " + getTable().getQualifiedName( dialect, defaultCatalog, defaultSchema )
+				final String tableName = getTable().getQualifiedName( dialect, defaultCatalog, defaultSchema );
-						+ constraintString;
+				return dialect.getAlterTableString( tableName ) + " " + constraintString;
 			}
 		}
 		return null;

hibernate-core/src/main/java/org/hibernate/mapping/ForeignKey.java

@@ -173,8 +173,8 @@ public class ForeignKey extends Constraint {
 	}
 	
 	public String sqlDropString(Dialect dialect, String defaultCatalog, String defaultSchema) {
-		final StringBuilder buf = new StringBuilder( "alter table " );
+		String tableName = getTable().getQualifiedName( dialect, defaultCatalog, defaultSchema );
-		buf.append( getTable().getQualifiedName( dialect, defaultCatalog, defaultSchema ) );
+		final StringBuilder buf = new StringBuilder( dialect.getAlterTableString( tableName ) );
 		buf.append( dialect.getDropForeignKeyString() );
 		if ( dialect.supportsIfExistsBeforeConstraintName() ) {
 			buf.append( "if exists " );

hibernate-core/src/main/java/org/hibernate/mapping/Table.java

@@ -447,13 +447,12 @@ public class Table implements RelationalModel, Serializable, Exportable {
 		
 		final JdbcEnvironment jdbcEnvironment = metadata.getDatabase().getJdbcEnvironment();
 
-		StringBuilder root = new StringBuilder( "alter table " )
+		final String tableName = jdbcEnvironment.getQualifiedObjectNameFormatter().format(
-				.append( 
+				tableInfo.getName(),
-						jdbcEnvironment.getQualifiedObjectNameFormatter().format(
+				dialect
-								tableInfo.getName(),
+		);
-								dialect
+
-						) 
+		StringBuilder root = new StringBuilder( dialect.getAlterTableString( tableName ) )
-				)
 				.append( ' ' )
 				.append( dialect.getAddColumnString() );
 

hibernate-core/src/main/java/org/hibernate/tool/schema/internal/StandardForeignKeyExporter.java

@@ -100,8 +100,7 @@ public class StandardForeignKeyExporter implements Exporter<ForeignKey> {
 				dialect
 		);
 
-		final StringBuilder buffer = new StringBuilder( "alter table " )
+		final StringBuilder buffer = new StringBuilder( dialect.getAlterTableString( sourceTableName ) )
-				.append( sourceTableName )
 				.append(
 						foreignKey.getKeyDefinition() != null ?
 								dialect.getAddForeignKeyConstraintString(
@@ -146,7 +145,8 @@ public class StandardForeignKeyExporter implements Exporter<ForeignKey> {
 				dialect
 		);
 		return new String[] {
-				"alter table " + sourceTableName + dialect.getDropForeignKeyString() + foreignKey.getName()
+				dialect.getAlterTableString( sourceTableName )
+						+ dialect.getDropForeignKeyString() + foreignKey.getName()
 		};
 	}
 }

hibernate-core/src/test/java/org/hibernate/dialect/PostgreSQL92DialectTestCase.java

@@ -0,0 +1,33 @@
+/*
+ * Hibernate, Relational Persistence for Idiomatic Java
+ *
+ * License: GNU Lesser General Public License (LGPL), version 2.1 or later.
+ * See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.
+ */
+package org.hibernate.dialect;
+
+import org.hibernate.testing.TestForIssue;
+import org.hibernate.testing.junit4.BaseUnitTestCase;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+/**
+ * Test case for PostgreSQL 9.2 specific things.
+ *
+ * @author Christoph Dreis
+ */
+public class PostgreSQL92DialectTestCase extends BaseUnitTestCase {
+
+	/**
+	 * Tests that getAlterTableString() will make use of IF EXISTS syntax
+	 */
+	@Test
+	@TestForIssue( jiraKey = "HHH-11647" )
+	public void testGetAlterTableString() {
+		PostgreSQL92Dialect dialect = new PostgreSQL92Dialect();
+
+		assertEquals("alter table if exists table_name", dialect.getAlterTableString( "table_name" ));
+	}
+
+}

hibernate-core/src/test/java/org/hibernate/test/schemaupdate/foreignkeys/ForeignKeyGenerationTest.java

@@ -161,8 +161,7 @@ public class ForeignKeyGenerationTest extends BaseUnitTestCase {
 		final List<String> sqlLines = Files.readAllLines( output.toPath(), Charset.defaultCharset() );
 		boolean found = false;
 		for ( String line : sqlLines ) {
-			if ( line.contains( expectedAlterTableStatement ) ) {
+			if ( line.matches( expectedAlterTableStatement ) ) {
-				found = true;
 				return;
 			}
 		}
@@ -187,7 +186,7 @@ public class ForeignKeyGenerationTest extends BaseUnitTestCase {
 		}
 
 		public String toSQL() {
-			return "alter table " + tableName + " add constraint " + fkConstraintName + " foreign key (" + fkColumnName + ") references " + referenceTableName;
+			return "alter table (?:if exists) " + tableName + " add constraint " + fkConstraintName + " foreign key \\(" + fkColumnName + "\\) references " + referenceTableName;
 		}
 	}
 

hibernate-core/src/test/java/org/hibernate/test/schemaupdate/foreignkeys/JoinedInheritanceForeignKeyTest.java

@@ -78,8 +78,7 @@ public class JoinedInheritanceForeignKeyTest extends BaseUnitTestCase {
 		final List<String> sqlLines = Files.readAllLines( output.toPath(), Charset.defaultCharset() );
 		boolean found = false;
 		for ( String line : sqlLines ) {
-			if ( line.contains( expectedAlterTableStatement ) ) {
+			if ( line.matches( expectedAlterTableStatement ) ) {
-				found = true;
 				return;
 			}
 		}
@@ -104,7 +103,7 @@ public class JoinedInheritanceForeignKeyTest extends BaseUnitTestCase {
 		}
 
 		public String toSQL() {
-			return "alter table " + tableName + " add constraint " + fkConstraintName + " foreign key (" + fkColumnName + ") references " + referenceTableName;
+			return "alter table (?:if exists) " + tableName + " add constraint " + fkConstraintName + " foreign key \\(" + fkColumnName + "\\) references " + referenceTableName;
 		}
 	}
 

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

@@ -18,6 +18,7 @@ import org.hibernate.boot.registry.StandardServiceRegistry;
 import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
 import org.hibernate.boot.spi.MetadataImplementor;
 import org.hibernate.dialect.DB2Dialect;
+import org.hibernate.dialect.PostgreSQL81Dialect;
 import org.hibernate.engine.jdbc.env.spi.JdbcEnvironment;
 import org.hibernate.tool.hbm2ddl.SchemaExport;
 import org.hibernate.tool.schema.TargetType;
@@ -73,7 +74,7 @@ public class SchemaCreationTest {
 		for ( String statement : sqlLines ) {
 			assertThat(
 					"Should not try to create the unique constraint for the non existing table element",
-					statement.toLowerCase().contains( "alter table element" ),
+					statement.toLowerCase().matches( "alter table (?:if exists) element" ),
 					is( false )
 			);
 			if (ssr.getService(JdbcEnvironment.class).getDialect() instanceof DB2Dialect) {
@@ -81,7 +82,14 @@ public class SchemaCreationTest {
 						&& statement.toLowerCase().contains("category (code)")) {
 					isUniqueConstraintCreated = true;
 				}
-			} else {
+			}
+			else if (ssr.getService(JdbcEnvironment.class).getDialect() instanceof PostgreSQL81Dialect) {
+				if (statement.toLowerCase().startsWith("alter table if exists category add constraint")
+						&& statement.toLowerCase().contains("unique (code)")) {
+					isUniqueConstraintCreated = true;
+				}
+			}
+			else {
 				if (statement.toLowerCase().startsWith("alter table category add constraint")
 						&& statement.toLowerCase().contains("unique (code)")) {
 					isUniqueConstraintCreated = true;

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

@@ -126,7 +126,7 @@ public class UniqueConstraintDropTest {
 
 	private boolean checkDropConstraint(String tableName, String columnName) throws IOException {
 		boolean matches = false;
-		String regex = "alter table " + tableName + " drop constraint";
+		String regex = "alter table (?:if exists) " + tableName + " drop constraint";
 
 		if ( getDialect().supportsIfExistsBeforeConstraintName() ) {
 			regex += " if exists";

hibernate-core/src/test/java/org/hibernate/test/schemaupdate/uniqueconstraint/UniqueConstraintGenerationTest.java

@@ -19,6 +19,7 @@ import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
 import org.hibernate.boot.spi.MetadataImplementor;
 import org.hibernate.cfg.Environment;
 import org.hibernate.dialect.DB2Dialect;
+import org.hibernate.dialect.PostgreSQL81Dialect;
 import org.hibernate.engine.jdbc.env.spi.JdbcEnvironment;
 import org.hibernate.tool.hbm2ddl.SchemaExport;
 import org.hibernate.tool.schema.TargetType;
@@ -70,7 +71,8 @@ public class UniqueConstraintGenerationTest {
 					isCreateUniqueIndexGenerated("test_entity_item", "item"),
 					is(true)
 			);
-		} else {
+		}
+		else {
 			assertThat(
 					"The test_entity_item table unique constraint has not been generated",
 					isUniqueConstraintGenerated("test_entity_item", "item"),
@@ -87,7 +89,7 @@ public class UniqueConstraintGenerationTest {
 
 	private boolean isUniqueConstraintGenerated(String tableName, String columnName) throws IOException {
 		boolean matches = false;
-		final String regex = "alter table " + tableName + " add constraint uk_(.)* unique \\(" + columnName + "\\)";
+		final String regex = "alter table (?:if exists) " + tableName + " add constraint uk_(.)* unique \\(" + columnName + "\\)";
 
 		final String fileContent = new String( Files.readAllBytes( output.toPath() ) ).toLowerCase();
 		final String[] split = fileContent.split( System.lineSeparator() );