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.rel.type.RelDataTypeSystem;
  import org.apache.calcite.rel.type.RelDataTypeSystemImpl;
  import org.apache.calcite.rex.RexNode;
  import org.apache.calcite.sql.SqlAbstractDateTimeLiteral;
  import org.apache.calcite.sql.SqlBasicTypeNameSpec;
  import org.apache.calcite.sql.SqlCall;
  import org.apache.calcite.sql.SqlDataTypeSpec;
  import org.apache.calcite.sql.SqlDateLiteral;
  import org.apache.calcite.sql.SqlDialect;
  import org.apache.calcite.sql.SqlLiteral;
  import org.apache.calcite.sql.SqlNode;
  import org.apache.calcite.sql.SqlTimeLiteral;
  import org.apache.calcite.sql.SqlTimestampLiteral;
  import org.apache.calcite.sql.SqlWriter;
  import org.apache.calcite.sql.fun.SqlStdOperatorTable;
  import org.apache.calcite.sql.parser.SqlParserPos;
  import org.apache.calcite.sql.type.SqlTypeName;
  import org.apache.calcite.util.RelToSqlConverterUtil;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import java.util.Locale;
  
  import static org.apache.calcite.util.RelToSqlConverterUtil.unparseBoolLiteralToCondition;
  
  import static java.util.Objects.requireNonNull;
  
  /**
   * A <code>SqlDialect</code> implementation for the ClickHouse database.
   */
  public class ClickHouseSqlDialect extends SqlDialect {
    public static final RelDataTypeSystem TYPE_SYSTEM =
        new RelDataTypeSystemImpl() {
          @Override public int getMaxPrecision(SqlTypeName typeName) {
            switch (typeName) {
            case DECIMAL:
              return 76;
            default:
              return super.getMaxPrecision(typeName);
            }
          }
  
          @Override public int getMaxScale(SqlTypeName typeName) {
            switch (typeName) {
            case DECIMAL:
              return 76;
            default:
              return super.getMaxScale(typeName);
            }
          }
  
          @Override public int getMaxNumericScale() {
            return getMaxScale(SqlTypeName.DECIMAL);
          }
        };
  
    public static final SqlDialect.Context DEFAULT_CONTEXT = SqlDialect.EMPTY_CONTEXT
        .withDatabaseProduct(SqlDialect.DatabaseProduct.CLICKHOUSE)
        .withIdentifierQuoteString("`")
        .withNullCollation(NullCollation.LOW)
        .withDataTypeSystem(TYPE_SYSTEM);
  
    public static final SqlDialect DEFAULT = new ClickHouseSqlDialect(DEFAULT_CONTEXT);
  
    /** Creates a ClickHouseSqlDialect. */
    public ClickHouseSqlDialect(Context context) {
      super(context);
    }
  
    @Override public boolean supportsApproxCountDistinct() {
      return true;
    }
  
    @Override public boolean supportsCharSet() {
      return false;
    }
  
    @Override public boolean supportsNestedAggregations() {
      return false;
    }
  
    @Override public boolean supportsWindowFunctions() {
      return false;
    }
  
    @Override public boolean supportsAliasedValues() {
      return false;
    }
  
    @Override public CalendarPolicy getCalendarPolicy() {
      return CalendarPolicy.SHIFT;
    }
  
    @Override public RexNode prepareUnparse(RexNode arg) {
      return RelToSqlConverterUtil.unparseIsTrueOrFalse(arg);
    }
  
    @Override public @Nullable SqlNode getCastSpec(RelDataType type) {
      SqlTypeName typeName = type.getSqlTypeName();
      switch (typeName) {
      case CHAR:
        return createSqlDataTypeSpecByName(
            String.format(Locale.ROOT, "FixedString(%s)",
                type.getPrecision()), typeName, type.isNullable());
      case VARCHAR:
        return createSqlDataTypeSpecByName("String", typeName, type.isNullable());
      case TINYINT:
        return createSqlDataTypeSpecByName("Int8", typeName, type.isNullable());
      case SMALLINT:
        return createSqlDataTypeSpecByName("Int16", typeName, type.isNullable());
      case INTEGER:
        return createSqlDataTypeSpecByName("Int32", typeName, type.isNullable());
      case BIGINT:
        return createSqlDataTypeSpecByName("Int64", typeName, type.isNullable());
      case REAL:
        return createSqlDataTypeSpecByName("Float32", typeName, type.isNullable());
      case FLOAT:
      case DOUBLE:
        return createSqlDataTypeSpecByName("Float64", typeName, type.isNullable());
      case DATE:
        return createSqlDataTypeSpecByName("Date", typeName, type.isNullable());
      case TIMESTAMP:
      case TIMESTAMP_WITH_LOCAL_TIME_ZONE:
        return createSqlDataTypeSpecByName("DateTime", typeName, type.isNullable());
      case MAP:
        return RelToSqlConverterUtil.getCastSpecClickHouseSqlMapType(this, type,
            SqlParserPos.ZERO);
      case ARRAY:
        return RelToSqlConverterUtil.getCastSpecClickHouseSqlArrayType(this, type,
            SqlParserPos.ZERO);
      case MULTISET:
        throw new UnsupportedOperationException("ClickHouse dialect does not support cast to "
            + type.getSqlTypeName());
      default:
        break;
      }
  
      return super.getCastSpec(type);
    }
  
    private static SqlDataTypeSpec createSqlDataTypeSpecByName(String typeAlias,
        SqlTypeName typeName, boolean isNullable) {
      if (isNullable) {
        typeAlias = "Nullable(" + typeAlias + ")";
      }
      String finalTypeAlias = typeAlias;
      SqlBasicTypeNameSpec spec = new SqlBasicTypeNameSpec(typeName, SqlParserPos.ZERO) {
        @Override public void unparse(SqlWriter writer, int leftPrec, int rightPrec) {
          // unparse as an identifier to ensure that type names are cased correctly
          writer.identifier(finalTypeAlias, true);
        }
      };
      return new SqlDataTypeSpec(spec, SqlParserPos.ZERO);
    }
  
    @Override public void unparseDateTimeLiteral(SqlWriter writer,
        SqlAbstractDateTimeLiteral literal, int leftPrec, int rightPrec) {
      String toFunc;
      if (literal instanceof SqlDateLiteral) {
        toFunc = "toDate";
      } else if (literal instanceof SqlTimestampLiteral) {
        toFunc = "toDateTime";
      } else if (literal instanceof SqlTimeLiteral) {
        toFunc = "toTime";
      } else {
        throw new RuntimeException("ClickHouse does not support DateTime literal: "
            + literal);
      }
  
      writer.literal(toFunc + "('" + literal.toFormattedString() + "')");
    }
  
    @Override public void unparseBoolLiteral(SqlWriter writer, SqlLiteral literal, int leftPrec,
        int rightPrec) {
      Boolean value = (Boolean) literal.getValue();
      if (value == null) {
        return;
      }
      unparseBoolLiteralToCondition(writer, value);
    }
  
    @Override public void unparseOffsetFetch(SqlWriter writer, @Nullable SqlNode offset,
        @Nullable SqlNode fetch) {
      requireNonNull(fetch, "fetch");
  
      writer.newlineAndIndent();
      final SqlWriter.Frame frame =
          writer.startList(SqlWriter.FrameTypeEnum.FETCH);
      writer.keyword("LIMIT");
  
      if (offset != null) {
        offset.unparse(writer, -1, -1);
        writer.sep(",", true);
      }
  
      fetch.unparse(writer, -1, -1);
      writer.endList(frame);
    }
  
    @Override public void unparseCall(SqlWriter writer, SqlCall call,
        int leftPrec, int rightPrec) {
      if (call.getOperator() == SqlStdOperatorTable.APPROX_COUNT_DISTINCT) {
        RelToSqlConverterUtil.specialOperatorByName("UNIQ")
            .unparse(writer, call, 0, 0);
        return;
      }
  
      switch (call.getKind()) {
      case MAP_VALUE_CONSTRUCTOR:
        writer.print(call.getOperator().getName().toLowerCase(Locale.ROOT));
        final SqlWriter.Frame mapFrame = writer.startList("(", ")");
        for (int i = 0; i < call.operandCount(); i++) {
          writer.sep(",");
          call.operand(i).unparse(writer, leftPrec, rightPrec);
        }
        writer.endList(mapFrame);
        break;
      case ARRAY_VALUE_CONSTRUCTOR:
        writer.print(call.getOperator().getName().toLowerCase(Locale.ROOT));
        final SqlWriter.Frame arrayFrame = writer.startList("(", ")");
        for (SqlNode operand : call.getOperandList()) {
          writer.sep(",");
          operand.unparse(writer, leftPrec, rightPrec);
        }
        writer.endList(arrayFrame);
        break;
      case FLOOR:
        if (call.operandCount() != 2) {
          super.unparseCall(writer, call, leftPrec, rightPrec);
          return;
        }
        unparseFloor(writer, call);
        break;
      case STARTS_WITH:
        writer.print("startsWith");
        final SqlWriter.Frame startList = writer.startList("(", ")");
        call.operand(0).unparse(writer, 0, 0);
        writer.sep(",");
        call.operand(1).unparse(writer, 0, 0);
        writer.endList(startList);
        break;
      case ENDS_WITH:
        writer.print("endsWith");
        final SqlWriter.Frame endsList = writer.startList("(", ")");
        call.operand(0).unparse(writer, 0, 0);
        writer.sep(",");
        call.operand(1).unparse(writer, 0, 0);
        writer.endList(endsList);
        break;
      case BITAND:
        writer.print("bitAnd");
        final SqlWriter.Frame bitAndList = writer.startList("(", ")");
        call.operand(0).unparse(writer, 0, 0);
        writer.sep(",");
        call.operand(1).unparse(writer, 0, 0);
        writer.endList(bitAndList);
        break;
      case BITOR:
        writer.print("bitOr");
        final SqlWriter.Frame bitOrList = writer.startList("(", ")");
        call.operand(0).unparse(writer, 0, 0);
        writer.sep(",");
        call.operand(1).unparse(writer, 0, 0);
        writer.endList(bitOrList);
        break;
      case BITXOR:
        writer.print("bitXor");
        final SqlWriter.Frame bitXorList = writer.startList("(", ")");
        call.operand(0).unparse(writer, 0, 0);
        writer.sep(",");
        call.operand(1).unparse(writer, 0, 0);
        writer.endList(bitXorList);
        break;
      case BITNOT:
        writer.print("bitNot");
        final SqlWriter.Frame bitNotList = writer.startList("(", ")");
        call.operand(0).unparse(writer, 0, 0);
        writer.endList(bitNotList);
        break;
      case COUNT:
        // CH returns NULL rather than 0 for COUNT(DISTINCT) of NULL values.
        // https://github.com/yandex/ClickHouse/issues/2494
        // Wrap the call in a CH specific coalesce (assumeNotNull).
        if (call.getFunctionQuantifier() != null
            && call.getFunctionQuantifier().toString().equals("DISTINCT")) {
          writer.print("assumeNotNull");
          SqlWriter.Frame frame = writer.startList("(", ")");
          super.unparseCall(writer, call, leftPrec, rightPrec);
          writer.endList(frame);
        } else {
          super.unparseCall(writer, call, leftPrec, rightPrec);
        }
        break;
      case EXTRACT:
        SqlLiteral node = call.operand(0);
        TimeUnitRange unit = node.getValueAs(TimeUnitRange.class);
        String funName;
        switch (unit) {
        case DOW:
          funName = "DAYOFWEEK";
          break;
        case DOY:
          funName = "DAYOFYEAR";
          break;
        case WEEK:
          funName = "toWeek";
          break;
        default:
          super.unparseCall(writer, call, leftPrec, rightPrec);
          return;
        }
        writer.print(funName);
        final SqlWriter.Frame frame = writer.startList("(", ")");
        call.operand(1).unparse(writer, 0, 0);
        writer.endList(frame);
        break;
      default:
        super.unparseCall(writer, call, leftPrec, rightPrec);
      }
    }
  
    /**
     * Unparses datetime floor for ClickHouse.
     *
     * @param writer Writer
     * @param call Call
     */
    private static void unparseFloor(SqlWriter writer, SqlCall call) {
      final SqlLiteral timeUnitNode = call.operand(1);
      TimeUnitRange unit = timeUnitNode.getValueAs(TimeUnitRange.class);
  
      String funName;
      switch (unit) {
      case YEAR:
        funName = "toStartOfYear";
        break;
      case MONTH:
        funName = "toStartOfMonth";
        break;
      case WEEK:
        funName = "toMonday";
        break;
      case DAY:
        funName = "toDate";
        break;
      case HOUR:
        funName = "toStartOfHour";
        break;
      case MINUTE:
        funName = "toStartOfMinute";
        break;
      case SECOND:
        funName = "toStartOfSecond";
        break;
      case MILLISECOND:
        funName = "toStartOfMillisecond";
        break;
      case MICROSECOND:
        funName = "toStartOfMicrosecond";
        break;
      case NANOSECOND:
        funName = "toStartOfNanosecond";
        break;
      default:
        throw new RuntimeException("ClickHouse does not support FLOOR for time unit: "
            + unit);
      }
  
      writer.print(funName);
      SqlWriter.Frame frame = writer.startList("(", ")");
      call.operand(0).unparse(writer, 0, 0);
      writer.endList(frame);
    }
  }
  