public CardinalityEstimate estimate()

in wayang-commons/wayang-core/src/main/java/org/apache/wayang/core/optimizer/cardinality/DefaultCardinalityEstimator.java [69:107]
35 lines of code
11 McCabe index (conditional complexity)

    public CardinalityEstimate estimate(OptimizationContext optimizationContext, CardinalityEstimate... inputEstimates) {
        assert inputEstimates.length == this.numInputs
                || (this.isAllowMoreInputs && inputEstimates.length > this.numInputs) :
                String.format("Received %d input estimates, require %d%s.",
                        inputEstimates.length, this.numInputs, this.isAllowMoreInputs ? "+" : "");

        if (this.numInputs == 0) {
            final long estimate = this.singlePointEstimator.applyAsLong(new long[0], optimizationContext.getConfiguration());
            return new CardinalityEstimate(estimate, estimate, this.certaintyProb);
        }

        long[] lowerAndUpperInputEstimates = this.extractEstimateValues(inputEstimates);

        long lowerEstimate = -1, upperEstimate = -1;
        long[] currentInputEstimates = new long[this.numInputs];
        final int maximumBitMaskValue = 1 << this.numInputs;
        for (long positionBitmask = 0; positionBitmask < maximumBitMaskValue; positionBitmask++) {
            for (int pos = 0; pos < this.numInputs; pos++) {
                int bit = (int) ((positionBitmask >>> pos) & 0x1);
                currentInputEstimates[pos] = lowerAndUpperInputEstimates[(pos << 1) + bit];
            }
            long currentEstimate = Math.max(
                    this.singlePointEstimator.applyAsLong(currentInputEstimates, optimizationContext.getConfiguration()),
                    0
            );
            if (lowerEstimate == -1 || currentEstimate < lowerEstimate) {
                lowerEstimate = currentEstimate;
            }
            if (upperEstimate == -1 || currentEstimate > upperEstimate) {
                upperEstimate = currentEstimate;
            }
        }

        double correctnessProb = this.certaintyProb * Arrays.stream(inputEstimates)
                .mapToDouble(CardinalityEstimate::getCorrectnessProbability)
                .min()
                .orElseThrow(IllegalStateException::new);
        return new CardinalityEstimate(lowerEstimate, upperEstimate, correctnessProb);
    }