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.fun;
  
  import org.apache.calcite.config.CalciteSystemProperty;
  import org.apache.calcite.rel.type.RelDataType;
  import org.apache.calcite.rel.type.RelDataTypeFactory;
  import org.apache.calcite.sql.SqlAggFunction;
  import org.apache.calcite.sql.SqlCall;
  import org.apache.calcite.sql.SqlFunctionCategory;
  import org.apache.calcite.sql.SqlKind;
  import org.apache.calcite.sql.SqlSplittableAggFunction;
  import org.apache.calcite.sql.SqlSyntax;
  import org.apache.calcite.sql.type.OperandTypes;
  import org.apache.calcite.sql.type.ReturnTypes;
  import org.apache.calcite.sql.type.SqlOperandTypeChecker;
  import org.apache.calcite.sql.type.SqlTypeName;
  import org.apache.calcite.sql.validate.SqlValidator;
  import org.apache.calcite.sql.validate.SqlValidatorScope;
  import org.apache.calcite.util.Optionality;
  
  import com.google.common.collect.ImmutableList;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import java.util.List;
  
  /**
   * Definition of the SQL <code>COUNT</code> aggregation function.
   *
   * <p><code>COUNT</code> is an aggregator which returns the number of rows which
   * have gone into it. With one argument (or more), it returns the number of rows
   * for which that argument (or all) is not <code>null</code>.
   */
  public class SqlCountAggFunction extends SqlAggFunction {
    //~ Constructors -----------------------------------------------------------
  
    public SqlCountAggFunction(String name) {
      this(name, CalciteSystemProperty.STRICT.value() ? OperandTypes.ANY : OperandTypes.ONE_OR_MORE);
    }
  
    public SqlCountAggFunction(String name,
        SqlOperandTypeChecker sqlOperandTypeChecker) {
      super(name, null, SqlKind.COUNT, ReturnTypes.BIGINT, null,
          sqlOperandTypeChecker, SqlFunctionCategory.NUMERIC, false, false,
          Optionality.FORBIDDEN);
    }
  
    //~ Methods ----------------------------------------------------------------
  
    @Override public SqlSyntax getSyntax() {
      return SqlSyntax.FUNCTION_STAR;
    }
  
    @SuppressWarnings("deprecation")
    @Override public List<RelDataType> getParameterTypes(RelDataTypeFactory typeFactory) {
      return ImmutableList.of(
          typeFactory.createTypeWithNullability(
              typeFactory.createSqlType(SqlTypeName.ANY), true));
    }
  
    @SuppressWarnings("deprecation")
    @Override public RelDataType getReturnType(RelDataTypeFactory typeFactory) {
      return typeFactory.createSqlType(SqlTypeName.BIGINT);
    }
  
    @Override public RelDataType deriveType(
        SqlValidator validator,
        SqlValidatorScope scope,
        SqlCall call) {
      // Check for COUNT(*) function.  If it is we don't
      // want to try and derive the "*"
      if (call.isCountStar()) {
        return validator.getTypeFactory().createSqlType(
            SqlTypeName.BIGINT);
      }
      return super.deriveType(validator, scope, call);
    }
  
    @Override public <T extends Object> @Nullable T unwrap(Class<T> clazz) {
      if (clazz.isInstance(SqlSplittableAggFunction.CountSplitter.INSTANCE)) {
        return clazz.cast(SqlSplittableAggFunction.CountSplitter.INSTANCE);
      }
      return super.unwrap(clazz);
    }
  
    @Override public SqlAggFunction getRollup() {
      return SqlStdOperatorTable.SUM0;
    }
  }
  