jon-wei commented on a change in pull request #7588: multi-value string column
support for expressions
URL: https://github.com/apache/incubator-druid/pull/7588#discussion_r290541208
##########
File path: core/src/main/java/org/apache/druid/math/expr/Function.java
##########
@@ -1453,4 +1515,425 @@ public ExprEval apply(List<Expr> args,
Expr.ObjectBinding bindings)
}
}
+ class StringToArrayFunction implements Function
+ {
+ @Override
+ public String name()
+ {
+ return "string_to_array";
+ }
+
+ void validateArguments(List<Expr> args)
+ {
+ if (args.size() != 2) {
+ throw new IAE("Function[%s] needs 2 argument", name());
+ }
+ }
+
+ @Override
+ public ExprEval apply(List<Expr> args, Expr.ObjectBinding bindings)
+ {
+ validateArguments(args);
+
+ final ExprEval expr = args.get(0).eval(bindings);
+ final String arrayString = expr.asString();
+ if (arrayString == null) {
+ return ExprEval.of(null);
+ }
+
+ final String split = args.get(1).eval(bindings).asString();
+ return ExprEval.ofStringArray(arrayString.split(split != null ? split :
""));
+ }
+
+ @Override
+ public Set<Expr> getScalarInputs(List<Expr> args)
+ {
+ validateArguments(args);
+ return ImmutableSet.copyOf(args);
+ }
+ }
+
+ /**
+ * Function that operates on array typed operands
+ */
+ interface ArrayFunction extends Function
+ {
+ default void validateArguments(List<Expr> args)
+ {
+ if (args.size() != 1) {
+ throw new IAE("Function[%s] needs 1 argument", name());
+ }
+ }
+
+ @Override
+ default Set<Expr> getArrayInputs(List<Expr> args)
+ {
+ validateArguments(args);
+ return ImmutableSet.of(args.get(0));
+ }
+
+ @Override
+ default Set<Expr> getScalarInputs(List<Expr> args)
+ {
+ return Collections.emptySet();
+ }
+ }
+
+ /**
+ * {@link ArraysFunction} that takes 1 array operand and 1 scalar operand
+ */
+ abstract class ArrayScalarFunction implements ArrayFunction
+ {
+ @Override
+ public void validateArguments(List<Expr> args)
+ {
+ if (args.size() != 2) {
+ throw new IAE("Function[%s] needs 2 argument", name());
+ }
+ }
+
+ @Override
+ public Set<Expr> getScalarInputs(List<Expr> args)
+ {
+ validateArguments(args);
+ return ImmutableSet.of(args.get(1));
+ }
+
+ @Override
+ public Set<Expr> getArrayInputs(List<Expr> args)
+ {
+ return ImmutableSet.of(args.get(0));
+ }
+
+ @Override
+ public ExprEval apply(List<Expr> args, Expr.ObjectBinding bindings)
+ {
+ validateArguments(args);
+ final ExprEval arrayExpr = args.get(0).eval(bindings);
+ final ExprEval scalarExpr = args.get(1).eval(bindings);
+ if (arrayExpr.asArray() == null) {
+ return ExprEval.of(null);
+ }
+ return doApply(arrayExpr, scalarExpr);
+ }
+
+ abstract ExprEval doApply(ExprEval arrayExpr, ExprEval scalarExpr);
+ }
+
+ /**
+ * {@link ArraysFunction} that takes 2 array operands
+ */
+ abstract class ArraysFunction implements ArrayFunction
+ {
+ @Override
+ public void validateArguments(List<Expr> args)
+ {
+ if (args.size() != 2) {
Review comment:
should this and other array-handling functions check `Expr.isArray()` in
`validateArguments`?
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