Set journal_mode on open to avoid concurrency issues.

Author: rkistner

cpp/ConnectionPool.cpp

@@ -26,26 +26,6 @@ ConnectionPool::ConnectionPool(std::string dbName, std::string docPath,
     readConnections[i] = new ConnectionState(
         dbName, docPath, SQLITE_OPEN_READONLY | SQLITE_OPEN_FULLMUTEX);
   }
-
-  if (true == isConcurrencyEnabled) {
-    // Write connection WAL setup
-    writeConnection.queueWork([](sqlite3 *db) {
-      sqliteExecuteLiteralWithDB(db, "PRAGMA journal_mode = WAL;");
-      sqliteExecuteLiteralWithDB(
-          db,
-          "PRAGMA journal_size_limit = 6291456"); // 6Mb 1.5x default checkpoint
-                                                  // size
-      // Default to normal on all connections
-      sqliteExecuteLiteralWithDB(db, "PRAGMA synchronous = NORMAL;");
-    });
-
-    // Read connections WAL setup
-    for (int i = 0; i < this->maxReads; i++) {
-      readConnections[i]->queueWork([](sqlite3 *db) {
-        sqliteExecuteLiteralWithDB(db, "PRAGMA synchronous = NORMAL;");
-      });
-    }
-  }
 };
 
 ConnectionPool::~ConnectionPool() {

cpp/ConnectionState.cpp

@@ -116,5 +116,29 @@ SQLiteOPResult genericSqliteOpenDb(string const dbName, string const docPath,
                           .errorMessage = sqlite3_errmsg(*db)};
   }
 
+  // Set journal mode directly when opening.
+  // This may have some overhead on the main thread,
+  // but prevents race conditions with multiple connections.
+  if (sqlOpenFlags & SQLITE_OPEN_READONLY) {
+    exit = sqlite3_exec(*db, "PRAGMA busy_timeout = 30000;"
+      // Default to normal on all connections
+      "PRAGMA synchronous = NORMAL;",
+      nullptr, nullptr, nullptr
+    );
+  } else {
+    exit = sqlite3_exec(*db, "PRAGMA busy_timeout = 30000;"
+      "PRAGMA journal_mode = WAL;"
+      // 6Mb 1.5x default checkpoint size
+      "PRAGMA journal_size_limit = 6291456;"
+      // Default to normal on all connections
+      "PRAGMA synchronous = NORMAL;",
+      nullptr, nullptr, nullptr
+    );
+  }
+  if (exit != SQLITE_OK) {
+    return SQLiteOPResult{.type = SQLiteError,
+                          .errorMessage = sqlite3_errmsg(*db)};
+  }
+
   return SQLiteOPResult{.type = SQLiteOk, .rowsAffected = 0};
 }