amrishlal commented on a change in pull request #7959:
URL: https://github.com/apache/pinot/pull/7959#discussion_r792997931
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File path:
pinot-broker/src/main/java/org/apache/pinot/broker/requesthandler/BaseBrokerRequestHandler.java
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@@ -1487,6 +1498,46 @@ static void updateColumnNames(String rawTableName,
PinotQuery pinotQuery, boolea
}
}
+ private static void expandStarExpressionToActualColumns(PinotQuery
pinotQuery, Map<String, String> columnNameMap,
+ Expression selectStarExpr) {
+ List<Expression> originalSelections = pinotQuery.getSelectList();
+ // Avoid using stream apis in query path because we have found that it has
poorer performance compared to
+ // regular apis.
+ Set<String> originallySelectedColumnNames = new HashSet<>();
+ for (Expression originalSelection : originalSelections) {
+ if (originalSelection.isSetIdentifier()) {
+
originallySelectedColumnNames.add(originalSelection.getIdentifier().getName());
+ }
+ }
+ List<Expression> newSelections = new ArrayList<>();
+ for (Expression selection : originalSelections) {
+ if (selection.equals(selectStarExpr)) {
+ //expand '*' to actual columns, exclude default virtual columns
+ for (String tableCol : columnNameMap.values()) {
+ //we exclude default virtual columns and those columns that are
already a part of originalSelections (to
+ // dedup columns that are selected multiple times)
Review comment:
@Jackie-Jiang mysql doesn't dudup in any of the cases listed above,
except that multiple stars are not allowed in the select list. I don't have
access to postgresql, but I believe (as @suddendust tested earlier) the
behavior is the same as mysql except that postgresql allows multiple stars in
the select list.
The w3cschools console might be custom UI logic (note how they change column
name for query `SELECT CustomerID, CustomerID, FROM Customers` without the use
of aliasing) . Nothing wrong with deduding per se and either approach would
work, but I think we need to maintain consistency. For example:
* if we are deduping select list, then shouldn't `select *, *` be also
deduped (w3c sql console is doing dudupe here)?
* if we decide to dedup `select *, *` then shouldn't `select playerID,
playerID` (existing functionality which is not being currently deduped) also be
deduced?
* what about `select playerID, *, playerID` - how will dudupe work in this
case? (since we currently don't dedupe `playerID, playerID` but will dedup
`playerID, *`)
* I am wondering if we have an example of an actual commercial database
that is doing dedup of select list?
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