SQL: small optimization for SQLDriver::escapeIdentifier()

Avoid a memmove (and replace it with a memcpy) by not using
QString::prepend() but create a completely new string object instead.

Change-Id: Ibdb4a9c6b15b96f1743d47e158ff0fb9b2048221
Reviewed-by: Andy Shaw <andy.shaw@qt.io>

6 files changed, 9 insertions, 8 deletions

diff --git a/src/plugins/sqldrivers/db2/qsql_db2.cpp b/src/plugins/sqldrivers/db2/qsql_db2.cpp
index c2ca844d9d..a18d7a84fa 100644
--- a/src/plugins/sqldrivers/db2/qsql_db2.cpp
+++ b/src/plugins/sqldrivers/db2/qsql_db2.cpp
@@ -1699,8 +1699,8 @@ QString QDB2Driver::escapeIdentifier(const QString &identifier, IdentifierType)
     QString res = identifier;
     if (!identifier.isEmpty() && !identifier.startsWith(u'"') && !identifier.endsWith(u'"') ) {
         res.replace(u'"', "\"\""_L1);
-        res.prepend(u'"').append(u'"');
         res.replace(u'.', "\".\""_L1);
+        res = u'"' + res + u'"';
     }
     return res;
 }
diff --git a/src/plugins/sqldrivers/ibase/qsql_ibase.cpp b/src/plugins/sqldrivers/ibase/qsql_ibase.cpp
index d228628c08..b92b91c5cb 100644
--- a/src/plugins/sqldrivers/ibase/qsql_ibase.cpp
+++ b/src/plugins/sqldrivers/ibase/qsql_ibase.cpp
@@ -1860,8 +1860,8 @@ QString QIBaseDriver::escapeIdentifier(const QString &identifier, IdentifierType
     QString res = identifier;
     if (!identifier.isEmpty() && !identifier.startsWith(u'"') && !identifier.endsWith(u'"') ) {
         res.replace(u'"', "\"\""_L1);
-        res.prepend(u'"').append(u'"');
         res.replace(u'.', "\".\""_L1);
+        res = u'"' + res + u'"';
     }
     return res;
 }
diff --git a/src/plugins/sqldrivers/oci/qsql_oci.cpp b/src/plugins/sqldrivers/oci/qsql_oci.cpp
index c7d68e73f1..3dfb4f38d8 100644
--- a/src/plugins/sqldrivers/oci/qsql_oci.cpp
+++ b/src/plugins/sqldrivers/oci/qsql_oci.cpp
@@ -2753,8 +2753,8 @@ QString QOCIDriver::escapeIdentifier(const QString &identifier, IdentifierType t
     QString res = identifier;
     if (!identifier.isEmpty() && !isIdentifierEscaped(identifier, type)) {
         res.replace(u'"', "\"\""_L1);
-        res.prepend(u'"').append(u'"');
         res.replace(u'.', "\".\""_L1);
+        res = u'"' + res + u'"';
     }
     return res;
 }
diff --git a/src/plugins/sqldrivers/odbc/qsql_odbc.cpp b/src/plugins/sqldrivers/odbc/qsql_odbc.cpp
index b0b5edbcc8..2d367afa7e 100644
--- a/src/plugins/sqldrivers/odbc/qsql_odbc.cpp
+++ b/src/plugins/sqldrivers/odbc/qsql_odbc.cpp
@@ -2598,9 +2598,10 @@ QString QODBCDriver::escapeIdentifier(const QString &identifier, IdentifierType)
     QChar quote = const_cast<QODBCDriverPrivate*>(d)->quoteChar();
     QString res = identifier;
     if (!identifier.isEmpty() && !identifier.startsWith(quote) && !identifier.endsWith(quote) ) {
-        res.replace(quote, QString(quote)+QString(quote));
-        res.prepend(quote).append(quote);
-        res.replace(u'.', QString(quote) + u'.' +QString(quote));
+        const QString quoteStr(quote);
+        res.replace(quote, quoteStr + quoteStr);
+        res.replace(u'.', quoteStr + u'.' + quoteStr);
+        res = quote + res + quote;
     }
     return res;
 }
diff --git a/src/plugins/sqldrivers/psql/qsql_psql.cpp b/src/plugins/sqldrivers/psql/qsql_psql.cpp
index 06a15bb14a..81d7e14444 100644
--- a/src/plugins/sqldrivers/psql/qsql_psql.cpp
+++ b/src/plugins/sqldrivers/psql/qsql_psql.cpp
@@ -1516,8 +1516,8 @@ QString QPSQLDriver::escapeIdentifier(const QString &identifier, IdentifierType)
     QString res = identifier;
     if (!identifier.isEmpty() && !identifier.startsWith(u'"') && !identifier.endsWith(u'"') ) {
         res.replace(u'"', "\"\""_L1);
-        res.prepend(u'"').append(u'"');
         res.replace(u'.', "\".\""_L1);
+        res = u'"' + res + u'"';
     }
     return res;
 }
diff --git a/src/plugins/sqldrivers/sqlite/qsql_sqlite.cpp b/src/plugins/sqldrivers/sqlite/qsql_sqlite.cpp
index 6812addae1..2933c68a9d 100644
--- a/src/plugins/sqldrivers/sqlite/qsql_sqlite.cpp
+++ b/src/plugins/sqldrivers/sqlite/qsql_sqlite.cpp
@@ -49,9 +49,9 @@ static QString _q_escapeIdentifier(const QString &identifier, QSqlDriver::Identi
         return res;
     if (!identifier.isEmpty() && !identifier.startsWith(u'"') && !identifier.endsWith(u'"')) {
         res.replace(u'"', "\"\""_L1);
-        res.prepend(u'"').append(u'"');
         if (type == QSqlDriver::TableName)
             res.replace(u'.', "\".\""_L1);
+        res = u'"' + res + u'"';
     }
     return res;
 }