HHH-20003: add Spanner temp table exporter

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

@@ -24,6 +24,8 @@
 import org.hibernate.dialect.pagination.LimitHandler;
 import org.hibernate.dialect.pagination.LimitOffsetLimitHandler;
 import org.hibernate.dialect.sql.ast.SpannerSqlAstTranslator;
+import org.hibernate.dialect.temptable.SpannerTemporaryTableExporter;
+import org.hibernate.dialect.temptable.TemporaryTableExporter;
 import org.hibernate.dialect.unique.UniqueDelegate;
 import org.hibernate.engine.jdbc.dialect.spi.DialectResolutionInfo;
 import org.hibernate.engine.jdbc.env.spi.IdentifierHelper;
@@ -99,6 +101,9 @@ public class SpannerDialect extends Dialect {
 
 	private final Exporter<Table> spannerTableExporter = new SpannerDialectTableExporter( this );
 
+	private final SpannerTemporaryTableExporter spannerTemporaryTableExporter = new SpannerTemporaryTableExporter(
+			this );
+
 	private static final LockingStrategy LOCKING_STRATEGY = new DoNothingLockingStrategy();
 
 	private static final EmptyExporter NOOP_EXPORTER = new EmptyExporter();
@@ -720,6 +725,11 @@ public String getAddPrimaryKeyConstraintString(String constraintName) {
 		throw new UnsupportedOperationException( "Cannot add primary key constraint in Cloud Spanner." );
 	}
 
+	@Override
+	public TemporaryTableExporter getTemporaryTableExporter() {
+		return spannerTemporaryTableExporter;
+	}
+
 	// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 	// Lock acquisition functions
 

hibernate-core/src/main/java/org/hibernate/dialect/temptable/SpannerTemporaryTableExporter.java

@@ -0,0 +1,78 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright Red Hat Inc. and Hibernate Authors
+ */
+package org.hibernate.dialect.temptable;
+
+import org.hibernate.dialect.SpannerDialect;
+import org.hibernate.engine.spi.SharedSessionContractImplementor;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.function.Function;
+
+/**
+ * Spanner-specific exporter for temporary tables.
+ * Spanner requires PRIMARY KEY definitions to be outside the column definition list.
+ * * Syntax: CREATE TABLE Name (Col Type) PRIMARY KEY (Col)
+ */
+public class SpannerTemporaryTableExporter extends StandardTemporaryTableExporter {
+
+	private final SpannerDialect dialect;
+
+	public SpannerTemporaryTableExporter(SpannerDialect dialect) {
+		super( dialect );
+		this.dialect = dialect;
+	}
+
+	@Override
+	public String getSqlCreateCommand(TemporaryTable temporaryTable) {
+		final StringBuilder buffer = new StringBuilder( dialect.getCreateTableString() )
+				.append( ' ' )
+				.append( temporaryTable.getQualifiedTableName() )
+				.append( " (" );
+		final List<String> primaryKeyColumnNames = new ArrayList<>();
+		boolean first = true;
+		for ( TemporaryTableColumn column : temporaryTable.getColumnsForExport() ) {
+			if ( first ) {
+				first = false;
+			}
+			else {
+				buffer.append( ", " );
+			}
+			buffer.append( column.getColumnName() ).append( ' ' );
+			final String databaseTypeName = column.getSqlTypeDefinition();
+			buffer.append( databaseTypeName );
+			if ( !column.isNullable() ) {
+				buffer.append( " not null" );
+			}
+			// Track PK
+			if ( column.isPrimaryKey() ) {
+				primaryKeyColumnNames.add( column.getColumnName() );
+			}
+		}
+		buffer.append( ')' );
+		// append primary key (outside the column declaration for Spanner)
+		// primary key () is still needed even if there are no primary key columns
+		buffer.append( " primary key (" );
+		if ( !primaryKeyColumnNames.isEmpty() ) {
+			buffer.append( String.join( ", ", primaryKeyColumnNames ) );
+		}
+		buffer.append( ')' );
+		return buffer.toString();
+	}
+
+	@Override
+	public String getSqlTruncateCommand(
+			TemporaryTable temporaryTable,
+			Function<SharedSessionContractImplementor, String> sessionUidAccess,
+			SharedSessionContractImplementor session) {
+		if ( temporaryTable.getSessionUidColumn() != null ) {
+			return super.getSqlTruncateCommand( temporaryTable, sessionUidAccess, session );
+		}
+		else {
+			return dialect.getTruncateTableStatement( temporaryTable.getQualifiedTableName() );
+		}
+	}
+
+}