Examples with IF com.facebook.presto.spi.relation.SpecialFormExpression.Form.IF used on opensource projects

Example 1 with IF

use of com.facebook.presto.spi.relation.SpecialFormExpression.Form.IF in project presto by prestodb.

the class RewriteAggregationIfToFilter method apply.

@Override
public Result apply(AggregationNode aggregationNode, Captures captures, Context context) {
    ProjectNode sourceProject = captures.get(CHILD);
    Set<Aggregation> aggregationsToRewrite = aggregationNode.getAggregations().values().stream().filter(aggregation -> shouldRewriteAggregation(aggregation, sourceProject)).collect(toImmutableSet());
    if (aggregationsToRewrite.isEmpty()) {
        return Result.empty();
    }
    context.getSession().getRuntimeStats().addMetricValue(REWRITE_AGGREGATION_IF_TO_FILTER_APPLIED, 1);
    // Get the corresponding assignments in the input project.
    // The aggregationReferences only has the aggregations to rewrite, thus the sourceAssignments only has IF/CAST(IF) expressions with NULL false results.
    // Multiple aggregations may reference the same input. We use a map to dedup them based on the VariableReferenceExpression, so that we only do the rewrite once per input
    // IF expression.
    // The order of sourceAssignments determines the order of generating the new variables for the IF conditions and results. We use a sorted map to get a deterministic
    // order based on the name of the VariableReferenceExpressions.
    Map<VariableReferenceExpression, RowExpression> sourceAssignments = aggregationsToRewrite.stream().map(aggregation -> (VariableReferenceExpression) aggregation.getArguments().get(0)).collect(toImmutableSortedMap(VariableReferenceExpression::compareTo, identity(), variable -> sourceProject.getAssignments().get(variable), (left, right) -> left));
    Assignments.Builder newAssignments = Assignments.builder();
    newAssignments.putAll(sourceProject.getAssignments());
    // Map from the aggregation reference to the IF condition reference which will be put in the mask.
    Map<VariableReferenceExpression, VariableReferenceExpression> aggregationReferenceToConditionReference = new HashMap<>();
    // Map from the aggregation reference to the IF result reference. This only contains the aggregates where the IF can be safely unwrapped.
    // E.g., SUM(IF(CARDINALITY(array) > 0, array[1])) will not be included in this map as array[1] can return errors if we unwrap the IF.
    Map<VariableReferenceExpression, VariableReferenceExpression> aggregationReferenceToIfResultReference = new HashMap<>();
    AggregationIfToFilterRewriteStrategy rewriteStrategy = getAggregationIfToFilterRewriteStrategy(context.getSession());
    for (Map.Entry<VariableReferenceExpression, RowExpression> entry : sourceAssignments.entrySet()) {
        VariableReferenceExpression outputVariable = entry.getKey();
        RowExpression rowExpression = entry.getValue();
        SpecialFormExpression ifExpression = (SpecialFormExpression) ((rowExpression instanceof CallExpression) ? ((CallExpression) rowExpression).getArguments().get(0) : rowExpression);
        RowExpression condition = ifExpression.getArguments().get(0);
        VariableReferenceExpression conditionReference = context.getVariableAllocator().newVariable(condition);
        newAssignments.put(conditionReference, condition);
        aggregationReferenceToConditionReference.put(outputVariable, conditionReference);
        if (canUnwrapIf(ifExpression, rewriteStrategy)) {
            RowExpression trueResult = ifExpression.getArguments().get(1);
            if (rowExpression instanceof CallExpression) {
                // Wrap the result with CAST().
                trueResult = new CallExpression(((CallExpression) rowExpression).getDisplayName(), ((CallExpression) rowExpression).getFunctionHandle(), rowExpression.getType(), ImmutableList.of(trueResult));
            }
            VariableReferenceExpression ifResultReference = context.getVariableAllocator().newVariable(trueResult);
            newAssignments.put(ifResultReference, trueResult);
            aggregationReferenceToIfResultReference.put(outputVariable, ifResultReference);
        }
    }
    // Build new aggregations.
    ImmutableMap.Builder<VariableReferenceExpression, Aggregation> aggregations = ImmutableMap.builder();
    // Stores the masks used to build the filter predicates. Use set to dedup the predicates.
    ImmutableSortedSet.Builder<VariableReferenceExpression> masks = ImmutableSortedSet.naturalOrder();
    for (Map.Entry<VariableReferenceExpression, Aggregation> entry : aggregationNode.getAggregations().entrySet()) {
        VariableReferenceExpression output = entry.getKey();
        Aggregation aggregation = entry.getValue();
        if (!aggregationsToRewrite.contains(aggregation)) {
            aggregations.put(output, aggregation);
            continue;
        }
        VariableReferenceExpression aggregationReference = (VariableReferenceExpression) aggregation.getArguments().get(0);
        CallExpression callExpression = aggregation.getCall();
        VariableReferenceExpression ifResultReference = aggregationReferenceToIfResultReference.get(aggregationReference);
        if (ifResultReference != null) {
            callExpression = new CallExpression(callExpression.getSourceLocation(), callExpression.getDisplayName(), callExpression.getFunctionHandle(), callExpression.getType(), ImmutableList.of(ifResultReference));
        }
        VariableReferenceExpression mask = aggregationReferenceToConditionReference.get(aggregationReference);
        aggregations.put(output, new Aggregation(callExpression, Optional.empty(), aggregation.getOrderBy(), aggregation.isDistinct(), Optional.of(aggregationReferenceToConditionReference.get(aggregationReference))));
        masks.add(mask);
    }
    RowExpression predicate = TRUE_CONSTANT;
    if (!aggregationNode.hasNonEmptyGroupingSet() && aggregationsToRewrite.size() == aggregationNode.getAggregations().size()) {
        // All aggregations are rewritten by this rule. We can add a filter with all the masks to make the query more efficient.
        predicate = or(masks.build());
    }
    return Result.ofPlanNode(new AggregationNode(aggregationNode.getSourceLocation(), context.getIdAllocator().getNextId(), new FilterNode(aggregationNode.getSourceLocation(), context.getIdAllocator().getNextId(), new ProjectNode(context.getIdAllocator().getNextId(), sourceProject.getSource(), newAssignments.build()), predicate), aggregations.build(), aggregationNode.getGroupingSets(), aggregationNode.getPreGroupedVariables(), aggregationNode.getStep(), aggregationNode.getHashVariable(), aggregationNode.getGroupIdVariable()));
}