content: /*
   * 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.TimeUnitRange;
  import org.apache.calcite.config.NullCollation;
  import org.apache.calcite.rel.type.RelDataType;
  import org.apache.calcite.sql.JoinType;
  import org.apache.calcite.sql.SqlAlienSystemTypeNameSpec;
  import org.apache.calcite.sql.SqlBasicCall;
  import org.apache.calcite.sql.SqlCall;
  import org.apache.calcite.sql.SqlDataTypeSpec;
  import org.apache.calcite.sql.SqlDialect;
  import org.apache.calcite.sql.SqlIdentifier;
  import org.apache.calcite.sql.SqlKind;
  import org.apache.calcite.sql.SqlLiteral;
  import org.apache.calcite.sql.SqlNode;
  import org.apache.calcite.sql.SqlNodeList;
  import org.apache.calcite.sql.SqlUtil;
  import org.apache.calcite.sql.SqlWriter;
  import org.apache.calcite.sql.fun.SqlCase;
  import org.apache.calcite.sql.fun.SqlFloorFunction;
  import org.apache.calcite.sql.fun.SqlLibraryOperators;
  import org.apache.calcite.sql.fun.SqlStdOperatorTable;
  import org.apache.calcite.sql.parser.SqlParserPos;
  import org.apache.calcite.util.RelToSqlConverterUtil;
  
  import com.google.common.collect.ImmutableList;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import static org.apache.calcite.util.RelToSqlConverterUtil.unparseHiveTrim;
  import static org.apache.calcite.util.RelToSqlConverterUtil.unparseSparkArrayAndMap;
  
  /**
   * A <code>SqlDialect</code> implementation for the APACHE SPARK database.
   */
  public class SparkSqlDialect extends SqlDialect {
    public static final SqlDialect.Context DEFAULT_CONTEXT = SqlDialect.EMPTY_CONTEXT
        .withDatabaseProduct(SqlDialect.DatabaseProduct.SPARK)
        .withIdentifierQuoteString("`")
        .withNullCollation(NullCollation.LOW);
  
    public static final SqlDialect DEFAULT = new SparkSqlDialect(DEFAULT_CONTEXT);
  
    /**
     * Creates a SparkSqlDialect.
     */
    public SparkSqlDialect(SqlDialect.Context context) {
      super(context);
    }
  
    @Override protected boolean allowsAs() {
      return false;
    }
  
    @Override public boolean supportsCharSet() {
      return false;
    }
  
    @Override public JoinType emulateJoinTypeForCrossJoin() {
      return JoinType.CROSS;
    }
  
    @Override public boolean supportsGroupByWithRollup() {
      return true;
    }
  
    @Override public boolean supportsNestedAggregations() {
      return false;
    }
  
    @Override public boolean supportsAggregateFunction(SqlKind kind) {
      switch (kind) {
      case AVG:
      case COUNT:
      case CUBE:
      case SUM:
      case SUM0:
      case MIN:
      case MAX:
      case ROLLUP:
        return true;
      default:
        break;
      }
      return false;
    }
  
    @Override public boolean supportsApproxCountDistinct() {
      return true;
    }
  
    @Override public boolean supportsGroupByWithCube() {
      return true;
    }
  
    @Override public boolean supportsTimestampPrecision() {
      return false;
    }
  
    @Override public void unparseOffsetFetch(SqlWriter writer, @Nullable SqlNode offset,
        @Nullable SqlNode fetch) {
      unparseFetchUsingLimit(writer, offset, fetch);
    }
  
    @Override public void unparseCall(SqlWriter writer, SqlCall call,
        int leftPrec, int rightPrec) {
      switch (call.getKind()) {
      case ARRAY_VALUE_CONSTRUCTOR:
      case MAP_VALUE_CONSTRUCTOR:
        unparseSparkArrayAndMap(writer, call, leftPrec, rightPrec);
        break;
      case STARTS_WITH:
        SqlCall starsWithCall = SqlLibraryOperators.STARTSWITH
            .createCall(SqlParserPos.ZERO, call.getOperandList());
        super.unparseCall(writer, starsWithCall, leftPrec, rightPrec);
        break;
      case ENDS_WITH:
        SqlCall endsWithCall = SqlLibraryOperators.ENDSWITH
            .createCall(SqlParserPos.ZERO, call.getOperandList());
        super.unparseCall(writer, endsWithCall, leftPrec, rightPrec);
        break;
      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;
      case TRIM:
        unparseHiveTrim(writer, call, leftPrec, rightPrec);
        break;
      case POSITION:
        SqlUtil.unparseFunctionSyntax(SqlStdOperatorTable.POSITION, writer, call, false);
        break;
      default:
        super.unparseCall(writer, call, leftPrec, rightPrec);
      }
    }
  
    @Override public @Nullable SqlNode getCastSpec(RelDataType type) {
      switch (type.getSqlTypeName()) {
      case VARCHAR:
        return new SqlDataTypeSpec(
            new SqlAlienSystemTypeNameSpec("STRING", type.getSqlTypeName(),
                SqlParserPos.ZERO), SqlParserPos.ZERO);
      case ARRAY:
        return RelToSqlConverterUtil.getCastSpecAngleBracketArrayType(this, type,
            SqlParserPos.ZERO);
      case MULTISET:
        throw new UnsupportedOperationException("Spark dialect does not support cast to "
            + type.getSqlTypeName());
      default:
        break;
      }
      return super.getCastSpec(type);
    }
  
    /**
     * Rewrite SINGLE_VALUE(result).
     *
     * <blockquote><pre>
     * CASE COUNT(*)
     * WHEN 0 THEN NULL
     * WHEN 1 THEN MIN(&lt;result&gt;)
     * ELSE RAISE_ERROR("more than one value in agg SINGLE_VALUE")
     * </pre></blockquote>
     *
     * <pre>RAISE_ERROR("more than one value in agg SINGLE_VALUE") will throw exception
     * when result includes more than one value.</pre>
     */
    @Override public SqlNode rewriteSingleValueExpr(SqlNode aggCall, RelDataType relDataType) {
      final SqlNode operand = ((SqlBasicCall) aggCall).operand(0);
      final SqlLiteral nullLiteral = SqlLiteral.createNull(SqlParserPos.ZERO);
      SqlNodeList sqlNodesList = new SqlNodeList(SqlParserPos.ZERO);
      sqlNodesList.add(
          SqlLiteral.createCharString("more than one value in agg SINGLE_VALUE", SqlParserPos.ZERO));
      final SqlNode caseExpr =
          new SqlCase(SqlParserPos.ZERO,
              SqlStdOperatorTable.COUNT.createCall(SqlParserPos.ZERO,
                  ImmutableList.of(SqlIdentifier.STAR)),
              SqlNodeList.of(
                  SqlLiteral.createExactNumeric("0", SqlParserPos.ZERO),
                  SqlLiteral.createExactNumeric("1", SqlParserPos.ZERO)),
              SqlNodeList.of(
                  nullLiteral,
                  SqlStdOperatorTable.MIN.createCall(SqlParserPos.ZERO, operand)),
              RelToSqlConverterUtil.specialOperatorByName("RAISE_ERROR").createCall(sqlNodesList));
      LOGGER.debug("SINGLE_VALUE rewritten into [{}]", caseExpr);
      return caseExpr;
    }
  
  }
  