core/src/main/java/org/apache/calcite/sql/dialect/PostgresqlSqlDialect.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,
 * 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.calcite.sql.dialect;

import org.apache.calcite.avatica.util.Casing;
import org.apache.calcite.avatica.util.TimeUnitRange;
import org.apache.calcite.rel.type.RelDataType;
import org.apache.calcite.rel.type.RelDataTypeSystem;
import org.apache.calcite.rel.type.RelDataTypeSystemImpl;
import org.apache.calcite.sql.SqlCall;
import org.apache.calcite.sql.SqlDataTypeSpec;
import org.apache.calcite.sql.SqlDialect;
import org.apache.calcite.sql.SqlLiteral;
import org.apache.calcite.sql.SqlNode;
import org.apache.calcite.sql.SqlUserDefinedTypeNameSpec;
import org.apache.calcite.sql.SqlWriter;
import org.apache.calcite.sql.fun.SqlFloorFunction;
import org.apache.calcite.sql.parser.SqlParserPos;
import org.apache.calcite.sql.type.SqlTypeName;

/**
 * A <code>SqlDialect</code> implementation for the PostgreSQL database.
 */
public class PostgresqlSqlDialect extends SqlDialect {
  /** PostgreSQL type system. */
  private static final RelDataTypeSystem POSTGRESQL_TYPE_SYSTEM =
      new RelDataTypeSystemImpl() {
        @Override public int getMaxPrecision(SqlTypeName typeName) {
          switch (typeName) {
          case VARCHAR:
            // From htup_details.h in postgresql:
            // MaxAttrSize is a somewhat arbitrary upper limit on the declared size of
            // data fields of char(n) and similar types.  It need not have anything
            // directly to do with the *actual* upper limit of varlena values, which
            // is currently 1Gb (see TOAST structures in postgres.h).  I've set it
            // at 10Mb which seems like a reasonable number --- tgl 8/6/00. */
            return 10 * 1024 * 1024;
          default:
            return super.getMaxPrecision(typeName);
          }
        }
      };

  public static final SqlDialect.Context DEFAULT_CONTEXT = SqlDialect.EMPTY_CONTEXT
      .withDatabaseProduct(SqlDialect.DatabaseProduct.POSTGRESQL)
      .withIdentifierQuoteString("\"")
      .withUnquotedCasing(Casing.TO_LOWER)
      .withDataTypeSystem(POSTGRESQL_TYPE_SYSTEM);

  public static final SqlDialect DEFAULT = new PostgresqlSqlDialect(DEFAULT_CONTEXT);

  /** Creates a PostgresqlSqlDialect. */
  public PostgresqlSqlDialect(Context context) {
    super(context);
  }

  @Override public boolean supportsCharSet() {
    return false;
  }

  @Override public SqlNode getCastSpec(RelDataType type) {
    String castSpec;
    switch (type.getSqlTypeName()) {
    case TINYINT:
      // Postgres has no tinyint (1 byte), so instead cast to smallint (2 bytes)
      castSpec = "_smallint";
      break;
    case DOUBLE:
      // Postgres has a double type but it is named differently
      castSpec = "_double precision";
      break;
    default:
      return super.getCastSpec(type);
    }

    return new SqlDataTypeSpec(
        new SqlUserDefinedTypeNameSpec(castSpec, SqlParserPos.ZERO),
        SqlParserPos.ZERO);
  }

  @Override public boolean requiresAliasForFromItems() {
    return true;
  }

  @Override public boolean supportsNestedAggregations() {
    return false;
  }

  @Override public void unparseCall(SqlWriter writer, SqlCall call,
      int leftPrec, int rightPrec) {
    switch (call.getKind()) {
    case FLOOR:
      if (call.operandCount() != 2) {
        super.unparseCall(writer, call, leftPrec, rightPrec);
        return;
      }

      final SqlLiteral timeUnitNode = call.operand(1);
      final TimeUnitRange timeUnit = timeUnitNode.getValueAs(TimeUnitRange.class);

      SqlCall call2 = SqlFloorFunction.replaceTimeUnitOperand(call, timeUnit.name(),
          timeUnitNode.getParserPosition());
      SqlFloorFunction.unparseDatetimeFunction(writer, call2, "DATE_TRUNC", false);
      break;

    default:
      super.unparseCall(writer, call, leftPrec, rightPrec);
    }
  }
}

// End PostgresqlSqlDialect.java