siddharthteotia commented on a change in pull request #4535: Implement DISTINCT
clause
URL: https://github.com/apache/incubator-pinot/pull/4535#discussion_r315338961
##########
File path:
pinot-common/src/main/java/org/apache/pinot/pql/parsers/pql2/ast/OutputColumnListAstNode.java
##########
@@ -41,8 +42,54 @@ public void addChild(AstNode childNode) {
}
}
+ private void validate() {
+ boolean identifierPresent = false;
+ boolean distinctPresent = false;
+ boolean aggregateFunctionPresent = false;
+ if (hasChildren()) {
+ for (AstNode child : getChildren()) {
+ if (child instanceof OutputColumnAstNode) {
+ if (child.hasChildren()) {
+ for (AstNode selectChild : child.getChildren()) {
+ if (selectChild instanceof IdentifierAstNode) {
+ if (distinctPresent) {
+ throw new Pql2CompilationException("Syntax error: SELECT
list columns should be part of DISTINCT clause");
+ } else if (aggregateFunctionPresent) {
+ throw new Pql2CompilationException("Syntax error:
Aggregation functions cannot be used with select list columns");
+ } else {
+ identifierPresent = true;
+ }
+ } else if (selectChild instanceof FunctionCallAstNode) {
+ if (((FunctionCallAstNode)
selectChild).getName().equalsIgnoreCase("distinct")) {
+ if (identifierPresent) {
+ throw new Pql2CompilationException("Syntax error: SELECT
list columns should be part of DISTINCT clause");
+ } else if (aggregateFunctionPresent) {
+ throw new Pql2CompilationException("Syntax error:
Aggregation functions cannot be used with DISTINCT clause");
+ } else if (distinctPresent) {
+ throw new Pql2CompilationException("Syntax error: DISTINCT
clause can be used only once in a query");
+ } else {
+ distinctPresent = true;
+ }
+ } else {
+ if (distinctPresent) {
+ throw new Pql2CompilationException("Syntax error:
Aggregation functions cannot be used with DISTINCT clause");
+ } else if (identifierPresent) {
+ throw new Pql2CompilationException("Syntax error:
Aggregation functions cannot be used with select list columns");
+ } else {
+ aggregateFunctionPresent = true;
+ }
+ }
+ }
+ }
+ }
+ }
+ }
+ }
+ }
+
@Override
public void updateBrokerRequest(BrokerRequest brokerRequest) {
+ validate();
Review comment:
I may have used a not so good function name to indicate the meaning of what
is being done here.. by validation I still meant to do further parsing and
syntax analysis to catch bad queries -- something that was mentioned in the
design doc as well to catch queries like following at parse time itself. That's
why I feel this should happen all the time
SELECT DISTINCT(col1), col2 FROM foo
SELECT col1, SUM(col2) FROM foo
Pql2CompilerTest.java has more tests for such situations...
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