contrib/storage-hbase/src/main/java/org/apache/drill/exec/store/hbase/HBasePushFilterIntoScan.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
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 * 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
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 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
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 * See the License for the specific language governing permissions and
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package org.apache.drill.exec.store.hbase;

import org.apache.calcite.plan.RelOptRuleCall;
import org.apache.calcite.plan.RelOptRuleOperand;
import org.apache.calcite.plan.RelOptUtil;
import org.apache.calcite.rel.RelNode;
import org.apache.calcite.rex.RexNode;
import org.apache.drill.common.expression.LogicalExpression;
import org.apache.drill.exec.planner.logical.DrillOptiq;
import org.apache.drill.exec.planner.logical.DrillParseContext;
import org.apache.drill.exec.planner.logical.RelOptHelper;
import org.apache.drill.exec.planner.physical.FilterPrel;
import org.apache.drill.exec.planner.physical.PrelUtil;
import org.apache.drill.exec.planner.physical.ProjectPrel;
import org.apache.drill.exec.planner.physical.ScanPrel;
import org.apache.drill.exec.store.StoragePluginOptimizerRule;

import com.google.common.collect.ImmutableList;

public abstract class HBasePushFilterIntoScan extends StoragePluginOptimizerRule {

  private HBasePushFilterIntoScan(RelOptRuleOperand operand, String description) {
    super(operand, description);
  }

  public static final StoragePluginOptimizerRule FILTER_ON_SCAN =
      new HBasePushFilterIntoScan(RelOptHelper.some(
          FilterPrel.class, RelOptHelper.any(ScanPrel.class)),
          "HBasePushFilterIntoScan:Filter_On_Scan") {

    @Override
    public void onMatch(RelOptRuleCall call) {
      final ScanPrel scan = (ScanPrel) call.rel(1);
      final FilterPrel filter = (FilterPrel) call.rel(0);
      final RexNode condition = filter.getCondition();

      HBaseGroupScan groupScan = (HBaseGroupScan)scan.getGroupScan();
      if (groupScan.isFilterPushedDown()) {
        /*
         * The rule can get triggered again due to the transformed "scan => filter" sequence
         * created by the earlier execution of this rule when we could not do a complete
         * conversion of Optiq Filter's condition to HBase Filter. In such cases, we rely upon
         * this flag to not do a re-processing of the rule on the already transformed call.
         */
        return;
      }

      doPushFilterToScan(call, filter, null, scan, groupScan, condition);
    }

    @Override
    public boolean matches(RelOptRuleCall call) {
      final ScanPrel scan = (ScanPrel) call.rel(1);
      if (scan.getGroupScan() instanceof HBaseGroupScan) {
        return super.matches(call);
      }
      return false;
    }
  };


  public static final StoragePluginOptimizerRule FILTER_ON_PROJECT = new HBasePushFilterIntoScan(RelOptHelper.some(FilterPrel.class, RelOptHelper.some(ProjectPrel.class, RelOptHelper.any(ScanPrel.class))), "HBasePushFilterIntoScan:Filter_On_Project") {

    @Override
    public void onMatch(RelOptRuleCall call) {
      final ScanPrel scan = (ScanPrel) call.rel(2);
      final ProjectPrel project = (ProjectPrel) call.rel(1);
      final FilterPrel filter = (FilterPrel) call.rel(0);

      HBaseGroupScan groupScan = (HBaseGroupScan)scan.getGroupScan();
      if (groupScan.isFilterPushedDown()) {
        /*
         * The rule can get triggered again due to the transformed "scan => filter" sequence
         * created by the earlier execution of this rule when we could not do a complete
         * conversion of Optiq Filter's condition to HBase Filter. In such cases, we rely upon
         * this flag to not do a re-processing of the rule on the already transformed call.
         */
         return;
      }

      // convert the filter to one that references the child of the project
      final RexNode condition =  RelOptUtil.pushPastProject(filter.getCondition(), project);

      doPushFilterToScan(call, filter, project, scan, groupScan, condition);
    }

    @Override
    public boolean matches(RelOptRuleCall call) {
      final ScanPrel scan = (ScanPrel) call.rel(2);
      if (scan.getGroupScan() instanceof HBaseGroupScan) {
        return super.matches(call);
      }
      return false;
    }
  };


  protected void doPushFilterToScan(final RelOptRuleCall call, final FilterPrel filter, final ProjectPrel project, final ScanPrel scan, final HBaseGroupScan groupScan, final RexNode condition) {

    final LogicalExpression conditionExp = DrillOptiq.toDrill(new DrillParseContext(PrelUtil.getPlannerSettings(call.getPlanner())), scan, condition);
    final HBaseFilterBuilder hbaseFilterBuilder = new HBaseFilterBuilder(groupScan, conditionExp);
    final HBaseScanSpec newScanSpec = hbaseFilterBuilder.parseTree();
    if (newScanSpec == null) {
      return; //no filter pushdown ==> No transformation.
    }

    final HBaseGroupScan newGroupsScan = new HBaseGroupScan(groupScan.getUserName(), groupScan.getStoragePlugin(),
        newScanSpec, groupScan.getColumns());
    newGroupsScan.setFilterPushedDown(true);

    final ScanPrel newScanPrel = new ScanPrel(scan.getCluster(), filter.getTraitSet(), newGroupsScan, scan.getRowType(), scan.getTable());

    // Depending on whether is a project in the middle, assign either scan or copy of project to childRel.
    final RelNode childRel = project == null ? newScanPrel : project.copy(project.getTraitSet(), ImmutableList.of(newScanPrel));

    if (hbaseFilterBuilder.isAllExpressionsConverted()) {
        /*
         * Since we could convert the entire filter condition expression into an HBase filter,
         * we can eliminate the filter operator altogether.
         */
      call.transformTo(childRel);
    } else {
      call.transformTo(filter.copy(filter.getTraitSet(), ImmutableList.of(childRel)));
    }
  }

}