Aaaaaaron commented on a change in pull request #2253:
URL: https://github.com/apache/calcite/pull/2253#discussion_r535300256
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File path: core/src/main/java/org/apache/calcite/rex/RexSimplify.java
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@@ -1698,6 +1699,113 @@ RexNode simplifyAnd2ForUnknownAsFalse(List<RexNode>
terms,
}
}
+ /**
+ * <p>Simplifies AND/OR condition that has common expressions,
+ * extracts and eliminates/merges them as much as possible.</p>
+ * <ul>
+ * <li>(a OR b) AND (a OR b OR c OR d) => (a OR b)
+ * <li>(a OR b OR c OR d) AND (a OR b OR e OR f) => (a OR b) OR ((c OR d)
AND (e OR f))
+
+ * <li>(a AND b) OR (a AND b AND c) => (a AND b)
+ * <li>(a AND b AND c AND d) OR (a AND b AND e AND f) =>
+ * (a AND b) AND ((c AND d) OR (e AND f))
+ * </ul>
+ * <p> The difference between {@link #simplifyAnd} is that {@link
#simplifyAnd} mainly
+ * simplifies expressions whose answer can be determined without evaluating
both sides,
+ * like: FALSE AND (xxx) => FALSE</p>
+ */
+ public RexNode eliminateCommonExprInCondition(RexNode node) {
+ if (!(node instanceof RexCall)) {
+ return node;
+ }
+ // Simplify children recursively
+ // so that when we simplify parent node
+ // the child node should be simplified
+ List<RexNode> operands = ((RexCall) node).getOperands();
+ List<RexNode> simplifiedChildren = operands.stream()
+ .map(this::eliminateCommonExprInCondition)
+ .collect(Collectors.toList());
+
+ switch (node.getKind()) {
+ case AND: {
+ // Split the children to get the disjunctive predicates.
+ List<List<RexNode>> disjunctions = simplifiedChildren.stream()
+ .map(RelOptUtil::disjunctions)
+ .collect(Collectors.toList());
+
+ // Find the common predict among the list by retainAll.
+ List<RexNode> common = new ArrayList<>(disjunctions.get(0));
+ disjunctions.forEach(common::retainAll);
+
+ if (common.isEmpty()) {
+ // no common, return the original but with child simplified
+ return and(simplifiedChildren);
+ }
+
+ // Get the predicates that without the common part.
+ disjunctions.forEach(p -> p.removeAll(common));
+
+ if (disjunctions.stream().anyMatch(List::isEmpty)) {
+ // (a || b) && (a || b || c || d) => (a || b)
+ return or(common);
+ }
+ // (a || b || c || d) && (a || b || e || f) =>
+ // (a || b) || ((c || d) && (e || f))
+ List<RexNode> splice = disjunctions.stream()
+ .map(this::or)
+ .collect(Collectors.toList());
+ return or(or(common), and(splice));
+ }
+ case OR: {
+ // Split the children to get the conjunctions predicates.
+ List<List<RexNode>> conjunctions = simplifiedChildren.stream()
+ .map(RelOptUtil::conjunctions)
+ .collect(Collectors.toList());
+
+ // Find the common predict among the list by retainAll.
+ List<RexNode> common = new ArrayList<>(conjunctions.get(0));
+ conjunctions.forEach(common::retainAll);
+
+ if (common.isEmpty()) {
+ // no common, return the original but with child simplified
+ return or(simplifiedChildren);
+ }
+
+ // Get the predicates that without the common part.
+ conjunctions.forEach(p -> p.removeAll(common));
+
+ if (conjunctions.stream().anyMatch(List::isEmpty)) {
+ // (a && b) || (a && b && c) => (a && b)
+ return and(common);
+ }
+ // (a && b && c && d) || (a && b && e && f) =>
+ // (a && b) && ((c && d) || (e && f))
+ List<RexNode> splice = conjunctions.stream()
+ .map(this::and)
+ .collect(Collectors.toList());
+ return and(and(common), or(splice));
+ }
+ default:
+ return node;
+ }
+ }
+
+ private RexNode and(RexNode... nodes) {
+ return and(ImmutableList.copyOf(nodes));
+ }
+
+ private RexNode and(List<RexNode> nodes) {
+ return RexUtil.composeConjunction(rexBuilder, nodes);
+ }
+
+ private RexNode or(RexNode... nodes) {
+ return or(ImmutableList.copyOf(nodes));
+ }
+
+ private RexNode or(List<RexNode> nodes) {
+ return RexUtil.composeDisjunction(rexBuilder, nodes);
+ }
Review comment:
Emmmm there is a problem if I put these methods to RexUtil, we had to
add RexBuilder to the method declare, pretty ugly, why I create these methods
instead of using composeDisjunction/composeConjunction is for people to
understand the cord more easily.
Given that these methods are private, would it be OK to put them just in
RexSimplify?
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