zzwqqq commented on code in PR #5385:
URL: https://github.com/apache/calcite/pull/5385#discussion_r4534566700
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core/src/main/java/org/apache/calcite/plan/RelOptUtil.java:
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@@ -287,6 +302,128 @@ public static List<CorrelationId>
getVariablesSetAndUsed(RelNode rel0,
return result;
}
+ /** Returns whether a relational expression, its inputs and sub-queries are
+ * deterministic according to their operator declarations.
+ *
+ * <p>Assumes parameters, correlation bindings, query context and table
contents
+ * stay fixed within the query. Function calls use
+ * {@link SqlOperator#isDeterministic()}, which allows query-stable functions
+ * such as {@code CURRENT_TIMESTAMP}. A {@link Sample} must declare
repeatability.
+ * Unknown relational operators return false. Planner wrappers are not
expanded.
+ *
+ * <p>Input order must also be stable where it affects the result. This
method
+ * does not establish that property, for example for an unordered FETCH.
+ * It does not trim fields or modify the expression.
+ */
+ public static boolean isDeterministic(RelNode rel) {
+ if (rel instanceof Sample
+ && !((Sample) rel).getSamplingParameters().isRepeatable()) {
+ return false;
+ }
+ if (rel instanceof Aggregate
+ || rel instanceof Window
+ || rel instanceof Match
+ || rel instanceof Project
+ || rel instanceof Filter
+ || rel instanceof Calc
+ || rel instanceof Join
+ || rel instanceof Correlate
+ || rel instanceof Sort
+ || rel instanceof SetOp
+ || rel instanceof Exchange
+ || rel instanceof TableScan
+ || rel instanceof Values
+ || rel instanceof TableFunctionScan
+ || rel instanceof Snapshot
+ || rel instanceof Collect
+ || rel instanceof Uncollect
+ || rel instanceof Sample) {
+ try {
+ if (!tryVisitExpressions(rel, DeterminismChecker.INSTANCE)) {
+ return false;
+ }
+ if (rel instanceof Aggregate) {
+ for (AggregateCall call : ((Aggregate) rel).getAggCallList()) {
+ if (!call.getAggregation().isDeterministic()) {
+ return false;
+ }
+ }
+ }
+ for (RelNode input : rel.getInputs()) {
+ if (!isDeterministic(input)) {
+ return false;
+ }
+ }
+ return true;
+ } catch (Util.FoundOne e) {
+ Util.swallow(e, null);
+ }
+ }
+ return false;
+ }
+
+ /** Visits a supported node's expression fields for read-only analysis.
Review Comment:
Yes. It visits the node's expression fields, but not its relational inputs.
The returned expressions are not applied to the node. I've clarified the
Javadoc.
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