thomasrebele commented on code in PR #6293:
URL: https://github.com/apache/hive/pull/6293#discussion_r2832376888
##########
ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/stats/FilterSelectivityEstimator.java:
##########
@@ -184,91 +188,284 @@ public Double visitCall(RexCall call) {
return selectivity;
}
+ /**
+ * If the cast can be removed, just return its operand and adjust the
boundaries if necessary.
+ *
+ * <p>
+ * In Hive, if a value cannot be represented by the cast, the result of
the cast is NULL,
+ * and therefore cannot fulfill the predicate. So the possible range of
the values
+ * is limited by the range of possible values of the type.
+ * </p>
+ *
+ * <p>
+ * Special care is taken to support the cast to DECIMAL(precision, scale):
+ * The cast to DECIMAL rounds the value the same way as {@link
RoundingMode#HALF_UP}.
+ * The boundaries are adjusted accordingly, without changing the semantics
of <code>inclusive</code>.
+ * </p>
+ *
+ * @param cast a RexCall of type {@link SqlKind#CAST}
+ * @param tableScan the table that provides the statistics
+ * @param boundaries indexes 0 and 1 are the boundaries of the range
predicate;
+ * indexes 2 and 3, if they exist, will be set to the
boundaries of the type range
+ * @param inclusive whether the respective boundary is inclusive or
exclusive.
+ * @return the operand if the cast can be removed, otherwise the cast itself
+ */
+ private RexNode removeCastIfPossible(RexCall cast, HiveTableScan tableScan,
float[] boundaries, boolean[] inclusive) {
+ RexNode op0 = cast.getOperands().getFirst();
+ if (!(op0 instanceof RexInputRef)) {
+ return cast;
+ }
+ int index = ((RexInputRef) op0).getIndex();
+ final List<ColStatistics> colStats =
tableScan.getColStat(Collections.singletonList(index));
+ if (colStats.isEmpty()) {
+ return cast;
+ }
+
+ // we need to check that the possible values of the input to the cast are
all within the type range of the cast
+ // otherwise the CAST introduces some modulo-like behavior (*)
+ ColStatistics colStat = colStats.getFirst();
+ ColStatistics.Range range = colStat.getRange();
+ if (range == null)
+ return cast;
+ if (range.minValue == null || Double.isNaN(range.minValue.doubleValue()))
+ return cast;
+ if (range.maxValue == null || Double.isNaN(range.maxValue.doubleValue()))
+ return cast;
+
+ String type = cast.getType().getSqlTypeName().getName();
+
+ double min;
+ double max;
+ switch (type.toLowerCase()) {
+ case serdeConstants.TINYINT_TYPE_NAME:
+ min = Byte.MIN_VALUE;
+ max = Byte.MAX_VALUE;
+ break;
+ case serdeConstants.SMALLINT_TYPE_NAME:
+ min = Short.MIN_VALUE;
+ max = Short.MAX_VALUE;
+ break;
+ case serdeConstants.INT_TYPE_NAME, "integer":
+ min = Integer.MIN_VALUE;
+ max = Integer.MAX_VALUE;
+ break;
+ case serdeConstants.BIGINT_TYPE_NAME, serdeConstants.TIMESTAMP_TYPE_NAME:
+ min = Long.MIN_VALUE;
+ max = Long.MAX_VALUE;
+ break;
+ case serdeConstants.FLOAT_TYPE_NAME:
+ min = -Float.MAX_VALUE;
+ max = Float.MAX_VALUE;
+ break;
+ case serdeConstants.DOUBLE_TYPE_NAME:
+ min = -Double.MAX_VALUE;
+ max = Double.MAX_VALUE;
+ break;
+ case serdeConstants.DECIMAL_TYPE_NAME:
+ min = -Double.MAX_VALUE;
+ max = Double.MAX_VALUE;
+ adjustBoundariesForDecimal(cast, boundaries, inclusive);
+ break;
+ default:
+ // unknown type, do not remove the cast
+ return cast;
+ }
+
+ // see (*)
+ if (range.minValue.doubleValue() < min)
+ return cast;
+ if (range.maxValue.doubleValue() > max)
+ return cast;
+
+ return op0;
+ }
+
+ /**
+ * Adjust the boundaries for a DECIMAL cast.
+ * <p>
+ * See {@link #removeCastIfPossible(RexCall, HiveTableScan, float[],
boolean[])}
+ * for an explanation of the parameters.
+ */
+ private static void adjustBoundariesForDecimal(RexCall cast, float[]
boundaries, boolean[] inclusive) {
+ // values outside the representable range are cast to NULL, so adapt the
boundaries
+ int precision = cast.getType().getPrecision();
+ int scale = cast.getType().getScale();
+ int digits = precision - scale;
+ // the cast does some rounding, i.e., CAST(99.9499 AS DECIMAL(3,1)) = 99.9
+ // but CAST(99.95 AS DECIMAL(3,1)) = NULL
+ float adjust = (float) (5 * Math.pow(10, -(scale + 1)));
+ // the range of values supported by the type is interval
[-typeRangeExtent, typeRangeExtent] (both inclusive)
+ // e.g., the typeRangeExt is 99.94999 for DECIMAL(3,1)
+ float typeRangeExtent = Math.nextDown((float) (Math.pow(10, digits) -
adjust));
+
+ // the resulting value of +- adjust would be rounded up, so in some cases
we need to use Math.nextDown
+ float adjusted1 = inclusive[0] ? boundaries[0] - adjust :
Math.nextDown(boundaries[0] + adjust);
+ float adjusted2 = inclusive[1] ? Math.nextDown(boundaries[1] + adjust) :
boundaries[1] - adjust;
+
+ float lowerUniverse = inclusive[0] ? -typeRangeExtent :
Math.nextDown(-typeRangeExtent);
+ float upperUniverse = inclusive[1] ? typeRangeExtent :
Math.nextUp(typeRangeExtent);
+ boundaries[0] = Math.max(adjusted1, lowerUniverse);
+ boundaries[1] = Math.min(adjusted2, upperUniverse);
+ if (boundaries.length >= 4) {
+ boundaries[2] = lowerUniverse;
+ boundaries[3] = upperUniverse;
+ }
+ }
+
private double computeRangePredicateSelectivity(RexCall call, SqlKind op) {
- final boolean isLiteralLeft =
call.getOperands().get(0).getKind().equals(SqlKind.LITERAL);
- final boolean isLiteralRight =
call.getOperands().get(1).getKind().equals(SqlKind.LITERAL);
- final boolean isInputRefLeft =
call.getOperands().get(0).getKind().equals(SqlKind.INPUT_REF);
- final boolean isInputRefRight =
call.getOperands().get(1).getKind().equals(SqlKind.INPUT_REF);
+ double defaultSelectivity = ((double) 1 / (double) 3);
+ if (!(childRel instanceof HiveTableScan)) {
+ return defaultSelectivity;
+ }
- if (childRel instanceof HiveTableScan && isLiteralLeft != isLiteralRight
&& isInputRefLeft != isInputRefRight) {
- final HiveTableScan t = (HiveTableScan) childRel;
- final int inputRefIndex = ((RexInputRef)
call.getOperands().get(isInputRefLeft ? 0 : 1)).getIndex();
- final List<ColStatistics> colStats =
t.getColStat(Collections.singletonList(inputRefIndex));
+ // search for the literal
+ List<RexNode> operands = call.getOperands();
+ final Optional<Float> leftLiteral = extractLiteral(operands.get(0));
+ final Optional<Float> rightLiteral = extractLiteral(operands.get(1));
+ if ((leftLiteral.isPresent()) == (rightLiteral.isPresent())) {
+ return defaultSelectivity;
+ }
+ int literalOpIdx = leftLiteral.isPresent() ? 0 : 1;
+
+ // analyze the predicate
+ float value = leftLiteral.orElseGet(rightLiteral::get);
+ int boundaryIdx;
+ boolean openBound = op == SqlKind.LESS_THAN || op == SqlKind.GREATER_THAN;
+ switch (op) {
+ case LESS_THAN, LESS_THAN_OR_EQUAL:
+ boundaryIdx = literalOpIdx;
+ break;
+ case GREATER_THAN, GREATER_THAN_OR_EQUAL:
+ boundaryIdx = 1 - literalOpIdx;
+ break;
+ default:
+ return defaultSelectivity;
+ }
+ float[] boundaries = new float[] { Float.NEGATIVE_INFINITY,
Float.POSITIVE_INFINITY };
+ boolean[] inclusive = new boolean[] { true, true };
+ inclusive[boundaryIdx] = !openBound;
+ boundaries[boundaryIdx] = value;
+
+ // extract the column index from the other operator
+ final HiveTableScan scan = (HiveTableScan) childRel;
+ int inputRefOpIndex = 1 - literalOpIdx;
+ RexNode node = operands.get(inputRefOpIndex);
+ if (node.getKind().equals(SqlKind.CAST)) {
+ node = removeCastIfPossible((RexCall) node, scan, boundaries, inclusive);
+ }
- if (!colStats.isEmpty() && isHistogramAvailable(colStats.get(0))) {
- final KllFloatsSketch kll =
KllFloatsSketch.heapify(Memory.wrap(colStats.get(0).getHistogram()));
- final Object boundValueObject = ((RexLiteral)
call.getOperands().get(isLiteralLeft ? 0 : 1)).getValue();
- final SqlTypeName typeName = call.getOperands().get(isInputRefLeft ? 0
: 1).getType().getSqlTypeName();
- float value = extractLiteral(typeName, boundValueObject);
- boolean closedBound = op.equals(SqlKind.LESS_THAN_OR_EQUAL) ||
op.equals(SqlKind.GREATER_THAN_OR_EQUAL);
-
- double selectivity;
- if (op.equals(SqlKind.LESS_THAN_OR_EQUAL) ||
op.equals(SqlKind.LESS_THAN)) {
- selectivity = closedBound ? lessThanOrEqualSelectivity(kll, value) :
lessThanSelectivity(kll, value);
- } else {
- selectivity = closedBound ? greaterThanOrEqualSelectivity(kll,
value) : greaterThanSelectivity(kll, value);
- }
+ int inputRefIndex = -1;
+ if (node.getKind().equals(SqlKind.INPUT_REF)) {
+ inputRefIndex = ((RexInputRef) node).getIndex();
+ }
- // selectivity does not account for null values, we multiply for the
number of non-null values (getN)
- // and we divide by the total (non-null + null values) to get the
overall selectivity.
- //
- // Example: consider a filter "col < 3", and the following table rows:
- // _____
- // | col |
- // |_____|
- // |1 |
- // |null |
- // |null |
- // |3 |
- // |4 |
- // -------
- // kll.getN() would be 3, selectivity 1/3, t.getTable().getRowCount() 5
- // so the final result would be 3 * 1/3 / 5 = 1/5, as expected.
- return kll.getN() * selectivity / t.getTable().getRowCount();
- }
+ if (inputRefIndex < 0) {
+ return defaultSelectivity;
+ }
+
+ final List<ColStatistics> colStats =
scan.getColStat(Collections.singletonList(inputRefIndex));
+ if (colStats.isEmpty() || !isHistogramAvailable(colStats.get(0))) {
+ return defaultSelectivity;
}
- return ((double) 1 / (double) 3);
+
+ // convert the condition to a range val1 <= x < val2 for
rangedSelectivity(...)
+ float left = inclusive[0] ? boundaries[0] : Math.nextUp(boundaries[0]);
+ float right = inclusive[1] ? Math.nextUp(boundaries[1]) : boundaries[1];
+
+ final KllFloatsSketch kll =
KllFloatsSketch.heapify(Memory.wrap(colStats.get(0).getHistogram()));
+ double rawSelectivity = rangedSelectivity(kll, left, right);
+
+ // rawSelectivity does not account for null values, we multiply for the
number of non-null values (getN)
+ // and we divide by the total (non-null + null values) to get the overall
rawSelectivity.
+ //
+ // Example: consider a filter "col < 3", and the following table rows:
+ // _____
+ // | col |
+ // |_____|
+ // |1 |
+ // |null |
+ // |null |
+ // |3 |
+ // |4 |
+ // -------
+ // kll.getN() would be 3, rawSelectivity 1/3,
scan.getTable().getRowCount() 5
+ // so the final result would be 3 * 1/3 / 5 = 1/5, as expected.
+ return kll.getN() * rawSelectivity / scan.getTable().getRowCount();
}
private Double computeBetweenPredicateSelectivity(RexCall call) {
- final boolean hasLiteralBool =
call.getOperands().get(0).getKind().equals(SqlKind.LITERAL);
- final boolean hasInputRef =
call.getOperands().get(1).getKind().equals(SqlKind.INPUT_REF);
- final boolean hasLiteralLeft =
call.getOperands().get(2).getKind().equals(SqlKind.LITERAL);
- final boolean hasLiteralRight =
call.getOperands().get(3).getKind().equals(SqlKind.LITERAL);
+ if (!(childRel instanceof HiveTableScan)) {
+ return computeFunctionSelectivity(call);
+ }
+
+ List<RexNode> operands = call.getOperands();
+ final boolean hasLiteralBool =
operands.get(0).getKind().equals(SqlKind.LITERAL);
+ Optional<Float> leftLiteral = extractLiteral(operands.get(2));
+ Optional<Float> rightLiteral = extractLiteral(operands.get(3));
+
+ if (hasLiteralBool && leftLiteral.isPresent() && rightLiteral.isPresent())
{
+ final HiveTableScan scan = (HiveTableScan) childRel;
+ float leftValue = leftLiteral.get();
+ float rightValue = rightLiteral.get();
+
+ final Object inverseBoolValueObject = ((RexLiteral)
operands.getFirst()).getValue();
+ boolean inverseBool =
Boolean.parseBoolean(inverseBoolValueObject.toString());
+ // when they are equal it's an equality predicate, we cannot handle it
as "BETWEEN"
+ if (Objects.equals(leftValue, rightValue)) {
+ return inverseBool ? computeNotEqualitySelectivity(call) :
computeFunctionSelectivity(call);
+ }
+
+ float[] boundaries = new float[] { leftValue, rightValue,
Float.NEGATIVE_INFINITY, Float.POSITIVE_INFINITY };
+ boolean[] inclusive = new boolean[] { true, true };
- if (childRel instanceof HiveTableScan && hasLiteralBool && hasInputRef &&
hasLiteralLeft && hasLiteralRight) {
- final HiveTableScan t = (HiveTableScan) childRel;
- final int inputRefIndex = ((RexInputRef)
call.getOperands().get(1)).getIndex();
- final List<ColStatistics> colStats =
t.getColStat(Collections.singletonList(inputRefIndex));
+ RexNode expr = operands.get(1); // expr to be checked by the BETWEEN
+ if (expr.getKind().equals(SqlKind.CAST)) {
+ expr = removeCastIfPossible((RexCall) expr, scan, boundaries,
inclusive);
+ }
+
+ int inputRefIndex = -1;
+ if (expr.getKind().equals(SqlKind.INPUT_REF)) {
+ inputRefIndex = ((RexInputRef) expr).getIndex();
+ }
+
+ if (inputRefIndex < 0) {
+ return computeFunctionSelectivity(call);
+ }
+ final List<ColStatistics> colStats =
scan.getColStat(Collections.singletonList(inputRefIndex));
if (!colStats.isEmpty() && isHistogramAvailable(colStats.get(0))) {
+ // convert the condition to a range val1 <= x < val2 for
rangedSelectivity(...)
+ boundaries[1] = Math.nextUp(boundaries[1]);
+ boundaries[3] = Math.nextUp(boundaries[3]);
+
final KllFloatsSketch kll =
KllFloatsSketch.heapify(Memory.wrap(colStats.get(0).getHistogram()));
- final SqlTypeName typeName =
call.getOperands().get(1).getType().getSqlTypeName();
- final Object inverseBoolValueObject = ((RexLiteral)
call.getOperands().get(0)).getValue();
- boolean inverseBool =
Boolean.parseBoolean(inverseBoolValueObject.toString());
- final Object leftBoundValueObject = ((RexLiteral)
call.getOperands().get(2)).getValue();
- float leftValue = extractLiteral(typeName, leftBoundValueObject);
- final Object rightBoundValueObject = ((RexLiteral)
call.getOperands().get(3)).getValue();
- float rightValue = extractLiteral(typeName, rightBoundValueObject);
- // when inverseBool == true, this is a NOT_BETWEEN and selectivity
must be inverted
+ double rawSelectivity = rangedSelectivity(kll, boundaries[0],
boundaries[1]);
if (inverseBool) {
- if (rightValue == leftValue) {
- return computeNotEqualitySelectivity(call);
- } else if (rightValue < leftValue) {
- return 1.0;
- }
- return 1.0 - (kll.getN() * betweenSelectivity(kll, leftValue,
rightValue) / t.getTable().getRowCount());
- }
- // when they are equal it's an equality predicate, we cannot handle it
as "between"
- if (Double.compare(leftValue, rightValue) != 0) {
- return kll.getN() * betweenSelectivity(kll, leftValue, rightValue) /
t.getTable().getRowCount();
+ // when inverseBool == true, this is a NOT_BETWEEN and selectivity
must be inverted
+ // if there's a cast, the inversion is with respect to its codomain
(range of the values of the cast)
+ double typeRangeSelectivity = rangedSelectivity(kll, boundaries[2],
boundaries[3]);
+ rawSelectivity = typeRangeSelectivity - rawSelectivity;
}
+ // rawSelectivity does not account for null values, so adjust them
+ // for a detailed explanation, see comment at
computeRangePredicateSelectivity
+ return kll.getN() * rawSelectivity / scan.getTable().getRowCount();
Review Comment:
Done.
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