liyafan82 commented on a change in pull request #2282:
URL: https://github.com/apache/calcite/pull/2282#discussion_r532346934
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File path: core/src/main/java/org/apache/calcite/rex/RexSimplify.java
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@@ -329,6 +336,93 @@ private RexNode simplifyGenericNode(RexCall e) {
return rexBuilder.makeCall(e.getType(), e.getOperator(), operands);
}
+ /**
+ * Try to find a literal with the given value in the input list.
+ */
+ private int findLiteralIndex(List<RexNode> operands, long value) {
+ for (int i = 0; i < operands.size(); i++) {
+ if (operands.get(i).isA(SqlKind.LITERAL)) {
+ Comparable comparable = ((RexLiteral) operands.get(i)).getValue();
+ if (comparable instanceof BigDecimal && ((BigDecimal)
comparable).longValue() == value) {
+ return i;
+ }
+ }
+ }
+ return -1;
+ }
+
+ private RexNode simplifyArithmetic(RexCall e) {
+ if (e.getType().getSqlTypeName().getFamily() != SqlTypeFamily.NUMERIC
+ || e.getOperands().stream()
+ .anyMatch(o -> e.getType().getSqlTypeName().getFamily() !=
SqlTypeFamily.NUMERIC)) {
+ // we only support simplifying numeric types
+ return simplifyGenericNode(e);
+ }
+
+ assert e.getOperands().size() == 2;
+
+ // if any operand is null, the result will be null
+ if (RexUtil.isNullLiteral(e.operands.get(0), true)
+ || RexUtil.isNullLiteral(e.operands.get(1), true)) {
+ return rexBuilder.makeNullLiteral(e.type);
+ }
+
+ switch (e.getKind()) {
+ case PLUS:
+ return simplifyPlus(e);
+ case MINUS:
+ return simplifyMinus(e);
+ case TIMES:
+ return simplifyMultiply(e);
+ case DIVIDE:
+ return simplifyDivide(e);
+ default:
+ throw new IllegalArgumentException("Unsupported arithmeitc operation " +
e.getKind());
+ }
+ }
+
+ private RexNode simplifyPlus(RexCall e) {
+ int zeroIndex = findLiteralIndex(e.operands, 0L);
+ if (zeroIndex >= 0) {
+ // return the other operand
+ RexNode other = e.getOperands().get((zeroIndex + 1) % 2);
+ return other.getType().equals(e.getType())
+ ? other : rexBuilder.makeCast(e.getType(), other);
+ }
+ return simplifyGenericNode(e);
+ }
+
+ private RexNode simplifyMinus(RexCall e) {
+ int zeroIndex = findLiteralIndex(e.operands, 0L);
+ if (zeroIndex == 1) {
+ RexNode leftOperand = e.getOperands().get(0);
+ return leftOperand.getType().equals(e.getType())
+ ? leftOperand : rexBuilder.makeCast(e.getType(), leftOperand);
Review comment:
Thanks for the suggestion.
There are some special cases for which this is not true. For example,
```
NaN - NaN = NaN
Inf - Inf = NaN
```
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