Minimize rereading of batches in FSTLocalDocumentsView documentsMatchingCollectionQuery (#1533)

Previously in `documentsMatchingCollectionQuery`, write batches were read three times; in fact, all relevant batches will always be contained inside `allMutationBatchesAffectingQuery` (which is also more efficient); the other two calls were redundant.

1 files changed, 10 insertions, 0 deletions

diff --git a/Firestore/core/src/firebase/firestore/model/base_path.h b/Firestore/core/src/firebase/firestore/model/base_path.h
index 7608829..31aaebb 100644
--- a/Firestore/core/src/firebase/firestore/model/base_path.h
+++ b/Firestore/core/src/firebase/firestore/model/base_path.h
@@ -139,6 +139,16 @@ class BasePath {
     return size() <= rhs.size() && std::equal(begin(), end(), rhs.begin());
   }
 
+  /**
+   * Returns true if the given argument is a direct child of this path.
+   *
+   * Empty path is a parent of any path that consists of a single segment.
+   */
+  bool IsImmediateParentOf(const T& potential_child) const {
+    return size() + 1 == potential_child.size() &&
+           std::equal(begin(), end(), potential_child.begin());
+  }
+
   bool operator==(const BasePath& rhs) const {
     return segments_ == rhs.segments_;
   }