Add migration script for regenerating CommentParticipationByAccount CF.

scripts/migrate/comment-participation.pig

@@ -0,0 +1,63 @@
+-- Backfill data for CommentParticipationByAccount CF.
+
+%default SCRIPT_ROOT 'udfs/dist/lib'
+%default INPUT 'input'
+%default OUTPUT 'output'
+
+
+REGISTER '$SCRIPT_ROOT/reddit-pig-udfs.jar';
+
+
+items =
+LOAD '$INPUT/comment.dump'
+    USING PigStorage()
+    AS (id:long,
+        ups:int,
+        downs:int,
+        deleted:chararray,
+        spam:chararray,
+        timestamp:double);
+
+
+data =
+LOAD '$INPUT/comment-data.dump'
+    USING PigStorage()
+    AS (id:long,
+        key:chararray,
+        value);
+
+
+grouped_with_data =
+COGROUP items BY id, data BY id;
+
+
+items_with_data =
+FOREACH grouped_with_data
+    GENERATE FLATTEN(items),
+             com.reddit.pig.MAKE_MAP(data.(key, value)) AS data;
+
+
+comments_unfiltered =
+FOREACH items_with_data
+    GENERATE (long)data#'link_id' as link_id,
+             (long)data#'author_id' as author_id;
+
+
+link_x_author_full =
+FILTER comments_unfiltered
+    BY link_id IS NOT NULL AND
+       author_id IS NOT NULL;
+
+
+link_x_author =
+DISTINCT link_x_author_full;
+
+
+columns =
+FOREACH link_x_author
+    GENERATE com.reddit.pig.TO_36(author_id) AS rowkey,
+             com.reddit.pig.TO_36(link_id) AS name,
+             '';
+
+
+STORE columns INTO '$OUTPUT/CommentParticipationByAccount/';