[GitHub] [cassandra] blerer commented on a change in pull request #1368: WIP: CASSANDRA-17190:Changes to add support for string concatenations through the + operator

[GitBox <gi...@apache.org>]

blerer commented on a change in pull request #1368:
URL: https://github.com/apache/cassandra/pull/1368#discussion_r772140067



##########
File path: src/java/org/apache/cassandra/cql3/functions/OperationFcts.java
##########
@@ -105,6 +106,22 @@ protected ByteBuffer executeOnNumerics(NumberType<?> resultType,
             {
                 return resultType.mod(leftType, left, rightType, right);
             }
+        },
+        CONCATENATION('+', "_concat")

Review comment:
       There is no need to add a new enum. You should simply implemente the  `excuteOnStrings` method in `ADD`. The internal name is hidden and does not play any important role.

##########
File path: src/java/org/apache/cassandra/db/marshal/StringType.java
##########
@@ -18,10 +18,29 @@
 
 package org.apache.cassandra.db.marshal;
 
+import org.apache.cassandra.utils.ByteBufferUtil;
+
+import java.io.UnsupportedEncodingException;
+import java.nio.ByteBuffer;
+import java.nio.charset.Charset;
+
 public abstract class StringType extends AbstractType<String>
 {
     protected StringType(ComparisonType comparisonType)
     {
         super(comparisonType);
     }
+
+    public abstract String charsetName();
+
+    public ByteBuffer concat(StringType leftType,
+                             ByteBuffer left,
+                             StringType rightType,
+                             ByteBuffer right) throws UnsupportedEncodingException
+    {
+        String leftS = new String(left.array(), leftType.charsetName());
+        String rightS = new String(right.array(), rightType.charsetName());
+
+        return ByteBufferUtil.bytes(leftS + rightS);
+    }

Review comment:
       {{ByteBuffer}} do not necessarily have array. If they direct buffer that code will not work. To get the `String`  value from the `ByteBuffer` you should use: `leftType.compose(left)` to convert a `String` back into a `ByteBuffer` you should use the `decompose` method.   ` return decompose(leftS + rightS);` 




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