Dwrite commented on code in PR #4810:
URL: https://github.com/apache/calcite/pull/4810#discussion_r2872881596
##########
core/src/main/java/org/apache/calcite/rel/rel2sql/RelToSqlConverter.java:
##########
@@ -604,14 +604,63 @@ private static boolean selectListRequired(Context
context) {
return false;
}
- /** Visits a Project; called by {@link #dispatch} via reflection. */
+ /**
+ * Extracts the table name from a SqlNode if it represents a simple table
reference.
+ * Returns null for complex nodes like subqueries or joins.
+ *
+ * <p>Examples:
+ * <ul>
+ * <li>"product" → "product"</li>
+ * <li>"foodmart.product" → "product"</li>
+ * <li>"SCOTT"."EMP" → "EMP"</li>
+ * <li>Subquery/Join/Other → null</li>
+ * </ul>
+ *
+ * @param node The SQL node to examine
+ * @return The table name if it's a simple identifier, null otherwise
+ */
+ private @Nullable String extractTableNameFromNode(SqlNode node) {
+ if (node instanceof SqlIdentifier) {
+ SqlIdentifier id = (SqlIdentifier) node;
+ // Return the last component (table name)
+ return id.names.get(id.names.size() - 1);
+ }
+
+ // All other cases: return null
+ return null;
+ }
+ /**
+ * Visits a Project; called by {@link #dispatch} via reflection.
+ */
public Result visit(Project e) {
// If the input is a Sort, wrap SELECT is not required.
final Result x;
+ final Set<CorrelationId> definedHere = e.getVariablesSet();
+ boolean pushed = !definedHere.isEmpty();
+
+ // Visit input node
+ Result inputResult;
if (e.getInput() instanceof Sort) {
- x = visitInput(e, 0);
+ inputResult = visitInput(e, 0);
+ } else {
+ inputResult = visitInput(e, 0, Clause.SELECT);
+ }
+
+ // If this Project defines correlations, fill in alias and force explicit
generation
+ if (pushed) {
+ String alias = inputResult.neededAlias;
+ if (alias != null) {
+ x = inputResult.resetAliasForCorrelation(alias,
e.getInput().getRowType());
+ } else {
+ alias = extractTableNameFromNode(inputResult.node);
+ if (alias == null) {
+ alias = "t";
Review Comment:
Updated. The priority is: Existing Alias > Table Name > 't'. By preserving
table names even in multi-level correlations, we minimize collisions and ensure
DML compatibility. 't' is strictly a fallback for anonymous relations, where
SQL scoping ensures safety.
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