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SQL Parser and Optimizer
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/*
 * 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 com.hazelcast.com.liance with
 * the License.  You may obtain a copy of the License at
 *
 * http://www.apache.com.hazelcast.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 com.hazelcast.org.apache.calcite.sql.validate;

import com.hazelcast.org.apache.calcite.sql.SqlCall;
import com.hazelcast.org.apache.calcite.sql.SqlFunction;
import com.hazelcast.org.apache.calcite.sql.SqlKind;
import com.hazelcast.org.apache.calcite.sql.SqlOperator;
import com.hazelcast.org.apache.calcite.sql.SqlOperatorTable;
import com.hazelcast.org.apache.calcite.sql.SqlSyntax;
import com.hazelcast.org.apache.calcite.sql.fun.SqlAbstractGroupFunction;
import com.hazelcast.org.apache.calcite.sql.util.SqlBasicVisitor;

import java.util.ArrayList;
import java.util.List;
import java.util.Objects;
import javax.annotation.Nullable;

/** Visitor that can find aggregate and windowed aggregate functions.
 *
 * @see AggFinder */
abstract class AggVisitor extends SqlBasicVisitor {
  protected final SqlOperatorTable opTab;
  /** Whether to find windowed aggregates. */
  protected final boolean over;
  protected final AggFinder delegate;
  /** Whether to find regular (non-windowed) aggregates. */
  protected final boolean aggregate;
  /** Whether to find group functions (e.g. {@code TUMBLE})
   * or group auxiliary functions (e.g. {@code TUMBLE_START}). */
  protected final boolean group;
  protected final SqlNameMatcher nameMatcher;

  /**
   * Creates an AggVisitor.
   *
   * @param opTab Operator table
   * @param over Whether to find windowed function calls {@code agg(x) OVER
   *             windowSpec}
   * @param aggregate Whether to find non-windowed aggregate calls
   * @param group Whether to find group functions (e.g. {@code TUMBLE})
   * @param delegate Finder to which to delegate when processing the arguments
   * @param nameMatcher Whether to match the agg function names case-sensitively
   */
  AggVisitor(SqlOperatorTable opTab, boolean over, boolean aggregate,
      boolean group, @Nullable AggFinder delegate, SqlNameMatcher nameMatcher) {
    this.group = group;
    this.over = over;
    this.aggregate = aggregate;
    this.delegate = delegate;
    this.opTab = Objects.requireNonNull(opTab);
    this.nameMatcher = Objects.requireNonNull(nameMatcher);
  }

  public Void visit(SqlCall call) {
    final SqlOperator operator = call.getOperator();
    // If nested aggregates disallowed or found an aggregate at invalid level
    if (operator.isAggregator()
        && !(operator instanceof SqlAbstractGroupFunction)
        && !operator.requiresOver()) {
      if (delegate != null) {
        return operator.acceptCall(delegate, call);
      }
      if (aggregate) {
        return found(call);
      }
    }
    if (group && operator.isGroup()) {
      return found(call);
    }
    // User-defined function may not be resolved yet.
    if (operator instanceof SqlFunction) {
      final SqlFunction sqlFunction = (SqlFunction) operator;
      if (sqlFunction.getFunctionType().isUserDefinedNotSpecificFunction()) {
        final List list = new ArrayList<>();
        opTab.lookupOperatorOverloads(sqlFunction.getSqlIdentifier(),
            sqlFunction.getFunctionType(), SqlSyntax.FUNCTION, list,
            nameMatcher);
        for (SqlOperator operator2 : list) {
          if (operator2.isAggregator() && !operator2.requiresOver()) {
            // If nested aggregates disallowed or found aggregate at invalid
            // level
            if (aggregate) {
              found(call);
            }
          }
        }
      }
    }
    if (call.isA(SqlKind.QUERY)) {
      // don't traverse into queries
      return null;
    }
    if (call.getKind() == SqlKind.WITHIN_GROUP) {
      if (aggregate) {
        return found(call);
      }
    }
    if (call.getKind() == SqlKind.OVER) {
      if (over) {
        return found(call);
      } else {
        // an aggregate function over a window is not an aggregate!
        return null;
      }
    }
    return super.visit(call);
  }

  protected abstract Void found(SqlCall call);
}