FrankChen021 commented on code in PR #20702:
URL: https://github.com/apache/druid/pull/20702#discussion_r4359554578
##########
sql/src/main/java/org/apache/druid/sql/calcite/planner/DruidSqlValidator.java:
##########
@@ -824,7 +826,46 @@ protected SqlNode performUnconditionalRewrites(SqlNode
node, final boolean under
}
}
- return super.performUnconditionalRewrites(node, underFrom);
+ if (node instanceof SqlSelect) {
+ aliasSelectItems((SqlSelect) node);
+ }
+
+ final SqlNode rewritten = super.performUnconditionalRewrites(node,
underFrom);
+
+ // Rewrite "x::TYPE" to standard CAST.
+ if (rewritten instanceof SqlCall cast
+ && SqlLibraryOperators.INFIX_CAST.equals(((SqlCall)
rewritten).getOperator())) {
+ return SqlStdOperatorTable.CAST.createCall(cast.getParserPosition(),
cast.getOperandList());
+ }
+
+ return rewritten;
+ }
+
+ /**
+ * Wraps select items in "AS" when {@link #deriveSelectItemAlias} has a
better name for them. This must run
+ * before other rewrites, since it looks at the syntax the user wrote.
+ */
+ private static void aliasSelectItems(final SqlSelect select)
+ {
+ final SqlNodeList selectList = select.getSelectList();
+ final List<String> aliases = new ArrayList<>(selectList.size());
+ final List<String> names = new ArrayList<>(selectList.size());
+ for (final SqlNode item : selectList) {
+ if (item instanceof SqlIdentifier && ((SqlIdentifier) item).isStar()) {
+ // Keep all defaults, since we can't tell which names the star expands
to.
+ return;
+ }
+ final String alias = deriveSelectItemAlias(item);
+ aliases.add(alias);
+ names.add(alias != null ? alias : SqlValidatorUtil.alias(item));
Review Comment:
[P2] Account for generated aliases in collision detection
**Finding:** `aliasSelectItems` uses the ordinal-less
`SqlValidatorUtil.alias(item)`, which returns null for literals and other
expressions even though Calcite later assigns them `EXPR$<ordinal>`. For
example, `SELECT 'x', EXPR$0::BIGINT FROM (SELECT 1 AS EXPR$0)` causes both
projected values to use `EXPR$0`; their differing STRING/LONG types can make
Druid row-signature construction fail, violating the documented duplicate-name
fallback.
**Suggestion:** Use ordinal-aware alias derivation, or otherwise reserve
Calcite's generated `EXPR$N` names, when building the collision set.
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