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https://issues.apache.org/jira/browse/METRON-1286?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16235730#comment-16235730
]
ASF GitHub Bot commented on METRON-1286:
----------------------------------------
Github user ottobackwards commented on a diff in the pull request:
https://github.com/apache/metron/pull/823#discussion_r148531977
--- Diff:
metron-stellar/stellar-common/src/main/java/org/apache/metron/stellar/dsl/functions/OrdinalFunctions.java
---
@@ -0,0 +1,75 @@
+package org.apache.metron.stellar.dsl.functions;
+
+import org.apache.metron.stellar.dsl.BaseStellarFunction;
+import org.apache.metron.stellar.dsl.Stellar;
+
+import java.util.Collections;
+import java.util.List;
+import java.util.stream.Collectors;
+
+public class OrdinalFunctions {
+
+ /**
+ * Stellar Function: MAX
+ * <p>
+ * Return the maximum value of a list of input values in a Stellar list
+ */
+ @Stellar(name = "MAX"
+ , description = "Returns the maximum value of a list of input
values"
+ , params = {"list_of_values - Stellar list of values to
evaluate. The list may only contain 1 type of object (only strings or only
numbers)" +
+ " and the objects must be comparable / ordinal"}
+ , returns = "The highest value in the list, null if the list
is empty or the input values could not be ordered")
+ public static class Max extends BaseStellarFunction {
+
+ @Override
+ public Object apply(List<Object> args) {
+ if (args.size() < 1 || args.get(0) == null) {
+ throw new IllegalStateException("MAX function requires at
least a Stellar list of values");
+ }
+ List list = (List<Object>) args.get(0);
+ return orderList(list, true);
+ }
+ }
+
+ /**
+ * Stellar Function: MIN
+ * <p>
+ * Return the minimum value of a list of input values in a Stellar list
+ */
+ @Stellar(name = "MIN"
+ , description = "Returns the minimum value of a list of input
values"
+ , params = {"list_of_values - Stellar list of values to
evaluate. The list may only contain 1 type of object (only strings or only
numbers)" +
+ " and the objects must be comparable / ordinal"}
+ , returns = "The lowest value in the list, null if the list is
empty or the input values could not be ordered")
+ public static class Min extends BaseStellarFunction {
+ @Override
+ public Object apply(List<Object> args) {
+ if (args.size() < 1 || args.get(0) == null) {
+ throw new IllegalStateException("MIN function requires at
least a Stellar list of values");
+ }
+ List list = (List<Object>) args.get(0);
+ return orderList(list, false);
+ }
+ }
+
+ private static Object orderList(List<Object> list, Boolean max) {
+ if (list.isEmpty()) {
+ return null;
+ }
+ List filteredList = (List<Object>) list.stream().filter(index ->
!(index == null)).collect(Collectors.toList());
+ if (filteredList.isEmpty()) {
+ return null;
+ }
--- End diff --
So, the functions document a requirement for Strings or Numbers, and
comparable/ordinal.
None of those things are verified here. If the function is going to
specify input, it needs to verify the input.
Following that, what happens if there is invalid input?
> Add MAX & MIN Stellar functions
> --------------------------------
>
> Key: METRON-1286
> URL: https://issues.apache.org/jira/browse/METRON-1286
> Project: Metron
> Issue Type: Improvement
> Affects Versions: 0.4.1
> Reporter: Jasper Knulst
> Priority: Minor
> Labels: features
> Fix For: 0.4.2
>
>
> Currently Stellar lacks straightforward MAX & MIN functions that take just a
> list of values as input.
> The functions STATS_MAX and STATS_MIN only take the internal Stellar
> statistics object as input.
> Having MAX and MIN will be easier and understandable to most
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