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.config.NullCollation;
  import org.apache.calcite.rel.type.RelDataType;
  import org.apache.calcite.rex.RexNode;
  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.SqlLiteral;
  import org.apache.calcite.sql.SqlNode;
  import org.apache.calcite.sql.SqlNodeList;
  import org.apache.calcite.sql.SqlOperator;
  import org.apache.calcite.sql.SqlSyntax;
  import org.apache.calcite.sql.SqlWriter;
  import org.apache.calcite.sql.fun.SqlCase;
  import org.apache.calcite.sql.fun.SqlStdOperatorTable;
  import org.apache.calcite.sql.parser.SqlParserPos;
  import org.apache.calcite.sql.type.AbstractSqlType;
  import org.apache.calcite.sql.type.BasicSqlType;
  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.unparseSparkArrayAndMap;
  
  /**
   * A <code>SqlDialect</code> implementation for the Apache Hive database.
   */
  public class HiveSqlDialect extends SqlDialect {
    public static final SqlDialect.Context DEFAULT_CONTEXT = SqlDialect.EMPTY_CONTEXT
        .withDatabaseProduct(SqlDialect.DatabaseProduct.HIVE)
        .withIdentifierQuoteString("`")
        .withNullCollation(NullCollation.LOW);
  
    public static final SqlDialect DEFAULT = new HiveSqlDialect(DEFAULT_CONTEXT);
  
    private final boolean emulateNullDirection;
  
    /** Creates a HiveSqlDialect. */
    public HiveSqlDialect(Context context) {
      super(context);
      // Since 2.1.0, Hive natively supports "NULLS FIRST" and "NULLS LAST".
      // See https://issues.apache.org/jira/browse/HIVE-12994.
      emulateNullDirection = (context.databaseMajorVersion() < 2)
          || (context.databaseMajorVersion() == 2
              && context.databaseMinorVersion() < 1);
    }
  
    @Override protected boolean allowsAs() {
      return false;
    }
  
    @Override public boolean requiresAliasForFromItems() {
      return true;
    }
  
    @Override public boolean supportsAliasedValues() {
      return false;
    }
  
    @Override public void unparseOffsetFetch(SqlWriter writer, @Nullable SqlNode offset,
        @Nullable SqlNode fetch) {
      unparseFetchUsingLimit(writer, offset, fetch);
    }
  
    @Override public @Nullable SqlNode emulateNullDirection(SqlNode node,
        boolean nullsFirst, boolean desc) {
      if (emulateNullDirection) {
        return emulateNullDirectionWithIsNull(node, nullsFirst, desc);
      }
  
      return null;
    }
  
    @Override public RexNode prepareUnparse(RexNode rexNode) {
      return RelToSqlConverterUtil.unparseIsTrueOrFalse(rexNode);
    }
  
    @Override public void unparseCall(final SqlWriter writer, final SqlCall call,
        final int leftPrec, final int rightPrec) {
      switch (call.getKind()) {
      case ARRAY_VALUE_CONSTRUCTOR:
      case MAP_VALUE_CONSTRUCTOR:
        unparseSparkArrayAndMap(writer, call, leftPrec, rightPrec);
        break;
      case POSITION:
        final SqlWriter.Frame frame = writer.startFunCall("INSTR");
        writer.sep(",");
        call.operand(1).unparse(writer, leftPrec, rightPrec);
        writer.sep(",");
        call.operand(0).unparse(writer, leftPrec, rightPrec);
        if (3 == call.operandCount()) {
          writer.sep(",");
          call.operand(2).unparse(writer, leftPrec, rightPrec);
        }
        if (4 == call.operandCount()) {
          writer.sep(",");
          call.operand(2).unparse(writer, leftPrec, rightPrec);
          writer.sep(",");
          call.operand(3).unparse(writer, leftPrec, rightPrec);
        }
        writer.endFunCall(frame);
        break;
      case MOD:
        SqlOperator op = SqlStdOperatorTable.PERCENT_REMAINDER;
        SqlSyntax.BINARY.unparse(writer, op, call, leftPrec, rightPrec);
        break;
      case TRIM:
        RelToSqlConverterUtil.unparseHiveTrim(writer, call, leftPrec, rightPrec);
        break;
      default:
        super.unparseCall(writer, call, leftPrec, rightPrec);
      }
    }
  
    @Override public boolean supportsCharSet() {
      return false;
    }
  
    @Override public boolean supportsGroupByWithRollup() {
      return true;
    }
  
    @Override public boolean supportsGroupByWithCube() {
      return true;
    }
  
    @Override public boolean supportsTimestampPrecision() {
      return false;
    }
  
    @Override public boolean supportsNestedAggregations() {
      return false;
    }
  
    @Override public @Nullable SqlNode getCastSpec(final RelDataType type) {
      if (type instanceof BasicSqlType) {
        switch (type.getSqlTypeName()) {
        case REAL:
          return new SqlDataTypeSpec(
              new SqlAlienSystemTypeNameSpec("FLOAT", type.getSqlTypeName(),
                  SqlParserPos.ZERO),
              SqlParserPos.ZERO);
        case INTEGER:
          SqlAlienSystemTypeNameSpec typeNameSpec =
              new SqlAlienSystemTypeNameSpec("INT", type.getSqlTypeName(),
                  SqlParserPos.ZERO);
          return new SqlDataTypeSpec(typeNameSpec, SqlParserPos.ZERO);
        case VARCHAR:
          if (type.getPrecision() == RelDataType.PRECISION_NOT_SPECIFIED) {
            return new SqlDataTypeSpec(
                new SqlAlienSystemTypeNameSpec("STRING", type.getSqlTypeName(),
                    SqlParserPos.ZERO), SqlParserPos.ZERO);
          }
          break;
        default:
          break;
        }
      }
  
      if (type instanceof AbstractSqlType) {
        switch (type.getSqlTypeName()) {
        case ARRAY:
        case MAP:
        case MULTISET:
          throw new UnsupportedOperationException("Hive 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 ASSERT_TRUE(false)
     * </pre></blockquote>
     *
     * <pre>ASSERT_TRUE(false) will throw assertion failed 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.createBoolean(false, 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("ASSERT_TRUE").createCall(sqlNodesList));
      LOGGER.debug("SINGLE_VALUE rewritten into [{}]", caseExpr);
      return caseExpr;
    }
  }
  