SqliteTableModel: Remove comments from SQL queries

MKleusberg · MKleusberg · commit 169eccbebb63 · 2013-09-06T14:08:33.000+02:00
Remove any single line comments from the SQL queries to fix all those problems ocurring when a query ending with such a comment is inserted into the COUNT query. Executing the query SELECT * FROM table -- comment would otherwise lead to this one being executed as well SELECT COUNT(*) FROM (SELECT * FROM table -- comment); This is obviously invalid SQL and therefore returns no data, sometimes even crashing the application, even though the original statement by the user is perfectly fine. The code used in this commit is a bit of a workaround and should be replaced as soon as there is a more complete SQL parser supporting SQL comments in our grammar tools. Closes sqlitebrowser#31.
diff --git a/src/sqlitetablemodel.cpp b/src/sqlitetablemodel.cpp
@@ -40,6 +40,38 @@ QString rtrimChar(const QString& s, QChar c) {
         r.chop(1);
     return r;
 }
+
+QString removeComments(QString s)
+{
+    // Feel free to fix all the bugs this probably contains or just replace this function entirely by
+    // a 'simple' regular expression. I know there're better ways to do this...
+
+    // This function removes any single line comments (starting with '--') from a given string. It does
+    // so by going through the string character by character and trying to keep track of wether we currently
+    // are in a string or identifier and only removing those parts starting with '--' which are in neither.
+
+    QChar lastChar = 0;
+    QList<QChar> stringChars;
+    for(int i=0;i<s.length();i++)
+    {
+        if(lastChar != '\\' && (s.at(i) == '\'' || s.at(i) == '"' || s.at(i) == '`'))
+        {
+            if(!stringChars.empty() && stringChars.last() == s.at(i))
+                stringChars.removeLast();
+            else if(!(!stringChars.empty() && (stringChars.last() != '\'' || stringChars.last() != '"')) || stringChars.empty())
+                stringChars.push_back(s.at(i));
+        } else if(stringChars.empty() && s.at(i) == '-' && lastChar == '-') {
+            if(s.contains('\n'))
+                return removeComments(s.remove(i-1, s.indexOf('\n', i)-i));
+            else
+                return s.left(i-1);
+        }
+
+        lastChar = s.at(i);
+    }
+
+    return s;
+}
 }
 
 void SqliteTableModel::setQuery(const QString& sQuery, bool dontClearHeaders)
@@ -52,7 +84,7 @@ void SqliteTableModel::setQuery(const QString& sQuery, bool dontClearHeaders)
     if(!m_db->isOpen())
         return;
 
-    m_sQuery = sQuery.trimmed();
+    m_sQuery = removeComments(sQuery).trimmed();
 
     // do a count query to get the full row count in a fast manner
     m_rowCount = getQueryRowCount();
