[jira] [Commented] (DRILL-8094) Support reverse truncation for split_part udf

["ASF GitHub Bot (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/DRILL-8094?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17466778#comment-17466778 ] 

ASF GitHub Bot commented on DRILL-8094:
---------------------------------------

jnturton commented on a change in pull request #2416:
URL: https://github.com/apache/drill/pull/2416#discussion_r776661535



##########
File path: exec/java-exec/src/main/java/org/apache/drill/exec/expr/fn/impl/StringFunctions.java
##########
@@ -416,16 +417,25 @@ public void setup() {
 
     @Override
     public void eval() {
-      if (index.value < 1) {
+      if (index.value == 0) {
         throw org.apache.drill.common.exceptions.UserException.functionError()
-          .message("Index in split_part must be positive, value provided was "
-            + index.value).build();
+          .message("Index in split_part can not be zero").build();
       }
       String inputString = org.apache.drill.exec.expr.fn.impl.
         StringFunctionHelpers.getStringFromVarCharHolder(in);
-      int arrayIndex = index.value - 1;
-      String result =
-              (String) com.google.common.collect.Iterables.get(splitter.split(inputString), arrayIndex, "");
+      String result = "";
+      if (index.value < 0) {
+        java.util.List<String> splits = splitter.splitToList(inputString);
+        int size = splits.size();
+        int arrayIndex = size + index.value;
+        if (arrayIndex >= 0) {

Review comment:
       What happens when arrayIndex < 0 here?  An informative error would be better than unitialised result data

##########
File path: exec/java-exec/src/main/java/org/apache/drill/exec/expr/fn/impl/StringFunctions.java
##########
@@ -416,16 +417,25 @@ public void setup() {
 
     @Override
     public void eval() {
-      if (index.value < 1) {
+      if (index.value == 0) {

Review comment:
       Sigh, 1-based indexing.  I think the logic you chose in this PR for non-positive index values is the best we can do, considering.




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> Support reverse truncation for split_part udf
> ---------------------------------------------
>
>                 Key: DRILL-8094
>                 URL: https://issues.apache.org/jira/browse/DRILL-8094
>             Project: Apache Drill
>          Issue Type: Improvement
>            Reporter: wtf
>            Priority: Minor
>
> suport split_part('a,b,c,d', ',' , -2, -1) = 'c,d' and split_part('a,b,c,d', ',' , -3) = 'b'



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