Keep track of number of queries in the query cache (#776)

* Implement schema versions

* Style fixes

* newlines, copyrights, assumptions

* Fix nullability

* Raw ptr -> shared_ptr

* kVersionTableGlobal -> kVersionGlobalTable

* Drop utils, move into static methods

* Drop extra include

* Add a few more comments

* Move version constant into migrations file

* formatting?

* Fix comment

* Split add and update queryData

* Work on adding targetCount

* More work on count

* Using shared_ptr

* Implement count for query cache

* use quotes

* Add cast

* Styling

* Revert year bump in copyright

* Add adversarial key to migration test

* Add comment

* Fix style

2 files changed, 32 insertions, 0 deletions

diff --git a/Firestore/Example/Tests/Local/FSTLevelDBMigrationsTests.mm b/Firestore/Example/Tests/Local/FSTLevelDBMigrationsTests.mm
index 8ef0e94..3559d5d 100644
--- a/Firestore/Example/Tests/Local/FSTLevelDBMigrationsTests.mm
+++ b/Firestore/Example/Tests/Local/FSTLevelDBMigrationsTests.mm
@@ -18,13 +18,18 @@
 #include <leveldb/db.h>
 
 #import "Firestore/Protos/objc/firestore/local/Target.pbobjc.h"
+#import "Firestore/Source/Local/FSTLevelDBKey.h"
 #import "Firestore/Source/Local/FSTLevelDBMigrations.h"
 #import "Firestore/Source/Local/FSTLevelDBQueryCache.h"
+#import "Firestore/Source/Local/FSTWriteGroup.h"
+
+#include "Firestore/core/src/firebase/firestore/util/ordered_code.h"
 
 #import "Firestore/Example/Tests/Local/FSTPersistenceTestHelpers.h"
 
 NS_ASSUME_NONNULL_BEGIN
 
+using firebase::firestore::util::OrderedCode;
 using leveldb::DB;
 using leveldb::Options;
 using leveldb::Status;
@@ -70,6 +75,30 @@ using leveldb::Status;
   XCTAssertGreaterThan(actual, 0, @"Expected to migrate to a schema version > 0");
 }
 
+- (void)testCountsQueries {
+  NSUInteger expected = 50;
+  FSTWriteGroup *group = [FSTWriteGroup groupWithAction:@"Setup"];
+  for (int i = 0; i < expected; i++) {
+    std::string key = [FSTLevelDBTargetKey keyWithTargetID:i];
+    [group setData:"dummy" forKey:key];
+  }
+  // Add a dummy entry after the targets to make sure the iteration is correctly bounded.
+  // Use a table that would sort logically right after that table 'target'.
+  std::string dummyKey;
+  // Magic number that indicates a table name follows. Needed to mimic the prefix to the target
+  // table.
+  OrderedCode::WriteSignedNumIncreasing(&dummyKey, 5);
+  OrderedCode::WriteString(&dummyKey, "targetA");
+  [group setData:"dummy" forKey:dummyKey];
+
+  Status status = [group writeToDB:_db];
+  XCTAssertTrue(status.ok(), @"Failed to write targets");
+
+  [FSTLevelDBMigrations runMigrationsOnDB:_db];
+  FSTPBTargetGlobal *metadata = [FSTLevelDBQueryCache readTargetMetadataFromDB:_db];
+  XCTAssertEqual(expected, metadata.targetCount, @"Failed to count all of the targets we added");
+}
+
 @end
 
 NS_ASSUME_NONNULL_END
diff --git a/Firestore/Example/Tests/Local/FSTQueryCacheTests.mm b/Firestore/Example/Tests/Local/FSTQueryCacheTests.mm
index 0c6a2a4..6ab655a 100644
--- a/Firestore/Example/Tests/Local/FSTQueryCacheTests.mm
+++ b/Firestore/Example/Tests/Local/FSTQueryCacheTests.mm
@@ -89,6 +89,7 @@ NS_ASSUME_NONNULL_BEGIN
 
   FSTQueryData *data2 = [self queryDataWithQuery:q2];
   [self addQueryData:data2];
+  XCTAssertEqual(2, [self.queryCache count]);
 
   XCTAssertEqualObjects([self.queryCache queryDataForQuery:q1], data1);
   XCTAssertEqualObjects([self.queryCache queryDataForQuery:q2], data2);
@@ -96,10 +97,12 @@ NS_ASSUME_NONNULL_BEGIN
   [self removeQueryData:data1];
   XCTAssertNil([self.queryCache queryDataForQuery:q1]);
   XCTAssertEqualObjects([self.queryCache queryDataForQuery:q2], data2);
+  XCTAssertEqual(1, [self.queryCache count]);
 
   [self removeQueryData:data2];
   XCTAssertNil([self.queryCache queryDataForQuery:q1]);
   XCTAssertNil([self.queryCache queryDataForQuery:q2]);
+  XCTAssertEqual(0, [self.queryCache count]);
 }
 
 - (void)testSetQueryToNewValue {