Jackie-Jiang commented on code in PR #17017:
URL: https://github.com/apache/pinot/pull/17017#discussion_r2434221012
##########
pinot-common/src/main/java/org/apache/pinot/common/utils/request/RequestUtils.java:
##########
@@ -664,4 +670,49 @@ public static void applyTimestampIndexOverrideHints(
}
}
}
+
+ /**
+ * Infers the expression type by recursively traversing the expression tree
for function calls. The provided schema
+ * is used to resolve the types for identifier expressions. Note that for
function calls, only scalar functions are
+ * supported here currently. Transform functions that don't have equivalent
scalar functions, and aggregation
+ * functions aren't supported and {@link ColumnDataType#UNKNOWN} will be
returned for them.
+ */
+ @Nullable
+ public static ColumnDataType inferExpressionType(@Nullable Expression
expression, Schema schema) {
+ if (expression == null) {
+ return null;
+ }
+
+ if (expression.isSetIdentifier()) {
+ String columnName = expression.getIdentifier().getName();
+ FieldSpec fieldSpec = schema.getFieldSpecFor(columnName);
+ if (fieldSpec == null) {
+ return ColumnDataType.UNKNOWN;
+ }
+ return ColumnDataType.fromDataType(fieldSpec.getDataType(),
fieldSpec.isSingleValueField());
+ }
+
+ if (expression.isSetLiteral()) {
+ LiteralContext literalContext = new
LiteralContext(expression.getLiteral());
+ return ColumnDataType.fromDataType(literalContext.getType(),
literalContext.isSingleValue());
+ }
+
+ if (expression.isSetFunctionCall()) {
+ Function fn = expression.getFunctionCall();
+ int numOperands = fn.getOperandsSize();
+ ColumnDataType[] argTypes = new ColumnDataType[numOperands];
+ for (int i = 0; i < numOperands; i++) {
+ ColumnDataType argType = inferExpressionType(fn.getOperands().get(i),
schema);
+ argTypes[i] = argType != null ? argType : ColumnDataType.UNKNOWN;
+ }
+ FunctionInfo functionInfo =
FunctionRegistry.lookupFunctionInfo(fn.getOperator(), argTypes);
+ if (functionInfo != null) {
+ Class<?> returnClass = functionInfo.getMethod().getReturnType();
Review Comment:
This is probably not enough, especially when a function returns `Object`
because various types of value can be returned by the same function based on
the argument, e.g. `JSON_EXTRACT_SCALAR`.
Ideally we want to use `SqlReturnTypeInference` to inference the return type
of a function. This info should be available from `PinotOperatorTable`. All the
working functions (at least in MSE) are already registered there
##########
pinot-common/src/main/java/org/apache/pinot/common/utils/request/RequestUtils.java:
##########
@@ -664,4 +670,49 @@ public static void applyTimestampIndexOverrideHints(
}
}
}
+
+ /**
+ * Infers the expression type by recursively traversing the expression tree
for function calls. The provided schema
+ * is used to resolve the types for identifier expressions. Note that for
function calls, only scalar functions are
+ * supported here currently. Transform functions that don't have equivalent
scalar functions, and aggregation
+ * functions aren't supported and {@link ColumnDataType#UNKNOWN} will be
returned for them.
+ */
+ @Nullable
+ public static ColumnDataType inferExpressionType(@Nullable Expression
expression, Schema schema) {
Review Comment:
I don't think we want to accept `null` expression here. If we don't accept
`null` expression, the return is also always not null
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