/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.drill.exec.planner.sql.handlers;
import java.util.List;
import net.hydromatic.optiq.tools.Planner;
import net.hydromatic.optiq.tools.RelConversionException;
import org.apache.drill.exec.ops.QueryContext;
import org.apache.drill.exec.planner.sql.parser.DrillParserUtil;
import org.apache.drill.exec.planner.sql.parser.SqlShowSchemas;
import org.eigenbase.sql.SqlIdentifier;
import org.eigenbase.sql.SqlNode;
import org.eigenbase.sql.SqlNodeList;
import org.eigenbase.sql.SqlSelect;
import org.eigenbase.sql.fun.SqlStdOperatorTable;
import org.eigenbase.sql.parser.SqlParserPos;
import com.google.common.collect.ImmutableList;
public class ShowSchemasHandler extends DefaultSqlHandler {
public ShowSchemasHandler(Planner planner, QueryContext context) { super(planner, context); }
/** Rewrite the parse tree as SELECT ... FROM INFORMATION_SCHEMA.SCHEMATA ... */
@Override
public SqlNode rewrite(SqlNode sqlNode) throws RelConversionException{
SqlShowSchemas node = unwrap(sqlNode, SqlShowSchemas.class);
List<SqlNode> selectList = ImmutableList.of((SqlNode) new SqlIdentifier("SCHEMA_NAME", SqlParserPos.ZERO));
SqlNode fromClause = new SqlIdentifier(
ImmutableList.of("INFORMATION_SCHEMA", "SCHEMATA"), null, SqlParserPos.ZERO, null);
SqlNode where = null;
final SqlNode likePattern = node.getLikePattern();
if (likePattern != null) {
where = DrillParserUtil.createCondition(new SqlIdentifier("SCHEMA_NAME", SqlParserPos.ZERO),
SqlStdOperatorTable.LIKE, likePattern);
} else if (node.getWhereClause() != null) {
where = node.getWhereClause();
}
return new SqlSelect(SqlParserPos.ZERO, null, new SqlNodeList(selectList, SqlParserPos.ZERO),
fromClause, where, null, null, null, null, null, null);
}
}