clintropolis commented on a change in pull request #7950: Add array_slice and
array_unshift function expr
URL: https://github.com/apache/incubator-druid/pull/7950#discussion_r296935909
##########
File path: core/src/main/java/org/apache/druid/math/expr/Function.java
##########
@@ -2062,4 +2062,111 @@ ExprEval doApply(ExprEval lhsExpr, ExprEval rhsExpr)
return ExprEval.bestEffortOf(any);
}
}
+
+ class ArraySliceFunction implements Function
+ {
+ @Override
+ public String name()
+ {
+ return "array_slice";
+ }
+
+ @Override
+ public void validateArguments(List<Expr> args)
+ {
+ if (args.size() != 2 && args.size() != 3) {
+ throw new IAE("Function[%s] needs 2 or 3 arguments", name());
+ }
+ }
+
+ @Override
+ public ExprEval apply(List<Expr> args, Expr.ObjectBinding bindings)
+ {
+ final ExprEval expr = args.get(0).eval(bindings);
+ final Object[] array = expr.asArray();
+ if (array == null) {
+ return ExprEval.of(null);
+ }
+
+ final int start = args.get(1).eval(bindings).asInt();
+ int end = array.length;
+ if (args.size() == 3) {
+ end = args.get(2).eval(bindings).asInt();
+ }
+
+ if (start < 0 || start > array.length || start > end) {
+ // Arrays.copyOfRange will throw exception in these cases
+ return ExprEval.of(null);
+ }
+
+ switch (expr.type()) {
+ case STRING:
+ case STRING_ARRAY:
+ return
ExprEval.ofStringArray(Arrays.copyOfRange(expr.asStringArray(), start, end));
+ case LONG:
+ case LONG_ARRAY:
+ return ExprEval.ofLongArray(Arrays.copyOfRange(expr.asLongArray(),
start, end));
+ case DOUBLE:
+ case DOUBLE_ARRAY:
+ return
ExprEval.ofDoubleArray(Arrays.copyOfRange(expr.asDoubleArray(), start, end));
+ }
+ throw new RE("Unable to slice to unknown type %s", expr.type());
+ }
+
+ @Override
+ public Set<Expr> getScalarInputs(List<Expr> args)
+ {
+ return ImmutableSet.of(args.get(1), args.get(2));
Review comment:
this should probably check if args length is 2 or 3?
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