QSqlRecord: (re)speedup indexOf(const QString& name)

While adding the possibility to access values for QSqlRecord with
decorated field names (table.field), some string-allocations were added
which created a remarkable slowdown. Replace the QString allocations
with QStringRef avoids those allocations and restores the speed for
normal operations (apart from on QString::indexOf() call and some
integer comparisons)

Task-number: QTBUG-65226
Change-Id: I9e458523891421abce9e4a7ed931fec000dcbe76
Reviewed-by: Andy Shaw <andy.shaw@qt.io>

1 files changed, 8 insertions, 7 deletions

diff --git a/src/sql/kernel/qsqlrecord.cpp b/src/sql/kernel/qsqlrecord.cpp
index 1c9ad5ec63..ecbe3eacdb 100644
--- a/src/sql/kernel/qsqlrecord.cpp
+++ b/src/sql/kernel/qsqlrecord.cpp
@@ -232,18 +232,19 @@ QString QSqlRecord::fieldName(int index) const
 
 int QSqlRecord::indexOf(const QString& name) const
 {
-    QString tableName;
-    QString fieldName = name;
+    QStringRef tableName;
+    QStringRef fieldName(&name);
     const int idx = name.indexOf(QLatin1Char('.'));
     if (idx != -1) {
-        tableName = name.left(idx);
-        fieldName = name.mid(idx + 1);
+        tableName = name.leftRef(idx);
+        fieldName = name.midRef(idx + 1);
     }
-    for (int i = 0; i < count(); ++i) {
+    const int cnt = count();
+    for (int i = 0; i < cnt; ++i) {
         // Check the passed in name first in case it is an alias using a dot.
         // Then check if both the table and field match when there is a table name specified.
-        const auto currentField = d->fields.at(i);
-        const auto currentFieldName = currentField.name();
+        const auto &currentField = d->fields.at(i);
+        const auto &currentFieldName = currentField.name();
         if (currentFieldName.compare(name, Qt::CaseInsensitive) == 0
             || (idx != -1 && currentFieldName.compare(fieldName, Qt::CaseInsensitive) == 0
                 && currentField.tableName().compare(tableName, Qt::CaseInsensitive) == 0)) {