Fix paginationType NONE to run further queries only if needed

If the first query to the index did not fill the full limit the caller
wants, we paginate to obtain more results. However, subsequent queries
are not needed if the previous query returned less results
than the limit.

This is a follow up of the change 413358 [1], that has reintroduced the
issue fixed in change 344695.

[1]: https://gerrit-review.googlesource.com/c/gerrit/+/413358/comment/85bca522_2b3552b2/

Bug: Issue 330195358
Release-Notes: Fix pagination to stop querying when there are no more results
Change-Id: Ie326f3628f5312a83bf83177a3fa5134f042b59a

1 files changed, 9 insertions, 16 deletions

diff --git a/java/com/google/gerrit/index/query/PaginatingSource.java b/java/com/google/gerrit/index/query/PaginatingSource.java
index 9ec64e63e0..d89fe66c14 100644
--- a/java/com/google/gerrit/index/query/PaginatingSource.java
+++ b/java/com/google/gerrit/index/query/PaginatingSource.java
@@ -55,12 +55,9 @@ public class PaginatingSource<T> implements DataSource<T> {
           List<T> r = new ArrayList<>();
           T last = null;
           int pageResultSize = 0;
-          boolean skipped = false;
           for (T data : buffer(resultSet)) {
             if (!isMatchable() || match(data)) {
               r.add(data);
-            } else {
-              skipped = true;
             }
             last = data;
             pageResultSize++;
@@ -69,16 +66,16 @@ public class PaginatingSource<T> implements DataSource<T> {
           if (last != null && source instanceof Paginated) {
             // Restart source and continue if we have not filled the
             // full limit the caller wants.
-            //
+            @SuppressWarnings("unchecked")
+            Paginated<T> p = (Paginated<T>) source;
+            QueryOptions opts = p.getOptions();
+            final int limit = opts.limit();
+
             // TODO: this fix is only for the stable branches and the real refactoring would be to
             // restore the logic
             // for the filtering in AndSource (L58 - 64) as per
             // https://gerrit-review.googlesource.com/c/gerrit/+/345634/9
             if (!indexConfig.paginationType().equals(PaginationType.NONE)) {
-              @SuppressWarnings("unchecked")
-              Paginated<T> p = (Paginated<T>) source;
-              QueryOptions opts = p.getOptions();
-              final int limit = opts.limit();
               int pageSize = opts.pageSize();
               int pageSizeMultiplier = opts.pageSizeMultiplier();
               Object searchAfter = resultSet.searchAfter();
@@ -100,20 +97,16 @@ public class PaginatingSource<T> implements DataSource<T> {
                 searchAfter = next.searchAfter();
               }
             } else {
-              @SuppressWarnings("unchecked")
-              Paginated<T> p = (Paginated<T>) source;
-              while (skipped && r.size() < p.getOptions().limit() + start) {
-                skipped = false;
-                ResultSet<T> next = p.restart(pageResultSize);
-
+              int nextStart = pageResultSize;
+              while (pageResultSize == limit && r.size() < limit) {
+                ResultSet<T> next = p.restart(nextStart);
                 for (T data : buffer(next)) {
                   if (match(data)) {
                     r.add(data);
-                  } else {
-                    skipped = true;
                   }
                   pageResultSize++;
                 }
+                nextStart += pageResultSize;
               }
             }
           }