contrib/storage-jdbc/src/main/java/org/apache/drill/exec/store/jdbc/clickhouse/ClickhouseJdbcImplementor.java

/*
 * 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,
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 * See the License for the specific language governing permissions and
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package org.apache.drill.exec.store.jdbc.clickhouse;

import org.apache.calcite.adapter.jdbc.JdbcTable;
import org.apache.calcite.plan.RelOptTable;
import org.apache.calcite.rel.RelNode;
import org.apache.calcite.rel.core.TableScan;
import org.apache.calcite.sql.parser.SqlParserPos;
import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableList;
import org.apache.calcite.adapter.java.JavaTypeFactory;
import org.apache.calcite.adapter.jdbc.JdbcImplementor;
import org.apache.calcite.sql.SqlDialect;
import org.apache.calcite.sql.SqlIdentifier;

import java.util.Iterator;

import static java.util.Objects.requireNonNull;

public class ClickhouseJdbcImplementor extends JdbcImplementor {
  public ClickhouseJdbcImplementor(SqlDialect dialect,
                                   JavaTypeFactory typeFactory) {
    super(dialect, typeFactory);
  }

  @Override
  public Result visit(TableScan scan) {
    SqlIdentifier sqlIdentifier = getSqlTargetTable(scan);
    Iterator<String> iter = sqlIdentifier.names.iterator();
    Preconditions.checkArgument(sqlIdentifier.names.size() == 3,
      "size of clickhouse table names:[%s] is not 3", sqlIdentifier.toString());
    iter.next();
    sqlIdentifier.setNames(ImmutableList.copyOf(iter), null);
    return result(sqlIdentifier, ImmutableList.of(Clause.FROM), scan, null);
  }

  private static SqlIdentifier getSqlTargetTable(RelNode e) {
    // Use the foreign catalog, schema and table names, if they exist,
    // rather than the qualified name of the shadow table in Calcite.
    RelOptTable table = requireNonNull(e.getTable());
    return table.maybeUnwrap(JdbcTable.class)
      .map(JdbcTable::tableName)
      .orElseGet(() ->
        new SqlIdentifier(table.getQualifiedName(), SqlParserPos.ZERO));
  }
}