Potential fix for ticket #477 (slowness opening postgres databases that

contain lots of views). Needs some testing, which I'll do in a day or
so.


git-svn-id: http://svn.osgeo.org/qgis/trunk@6610 c8812cc2-4d05-0410-92ff-de0c093fc19c

Author: g_j_m

src/providers/postgres/qgspostgresprovider.cpp

@@ -1159,8 +1159,9 @@ void QgsPostgresProvider::findColumns(tableCols& cols)
     "	nt.nspname AS table_schema, "
     "	t.relname AS table_name, "
     "	a.attname AS column_name, "
-    "	t.relkind as table_type, "
-    "	typ.typname as column_type "
+    "	t.relkind AS table_type, "
+    "	typ.typname AS column_type, "
+    "   vs.definition AS view_definition "
     "FROM "
     "	pg_namespace nv, "
     "	pg_class v, "
@@ -1170,7 +1171,8 @@ void QgsPostgresProvider::findColumns(tableCols& cols)
     "	pg_namespace nt, "
     "	pg_attribute a,"
     "	pg_user u, "
-    "	pg_type typ "
+    "	pg_type typ, "
+    "   pg_views vs "
     "WHERE "
     "	nv.oid = v.relnamespace AND "
     "	v.relkind = 'v'::\"char\" AND "
@@ -1188,7 +1190,9 @@ void QgsPostgresProvider::findColumns(tableCols& cols)
     "	t.oid = a.attrelid AND "
     "	dt.refobjsubid = a.attnum AND "
     "	nv.nspname NOT IN ('pg_catalog', 'information_schema' ) AND "
-    "	a.atttypid = typ.oid";
+    "	a.atttypid = typ.oid AND "
+    "   nv.nspname = vs.schemaname AND "
+    "   v.relname = vs.viewname";
 
   // A structure to store the results of the above sql.
   typedef std::map<QString, TT> columnRelationsType;
@@ -1213,41 +1217,24 @@ void QgsPostgresProvider::findColumns(tableCols& cols)
     temp.column_name      = PQgetvalue(result, i, 5);
     temp.table_type       = PQgetvalue(result, i, 6);
     temp.column_type      = PQgetvalue(result, i, 7);
+    QString viewDef       = PQgetvalue(result, i, 8);
 
     // BUT, the above SQL doesn't always give the correct value for the view 
     // column name (that's because that information isn't available directly 
     // from the database), mainly when the view column name has been renamed 
     // using 'AS'. To fix this we need to look in the view definition and 
     // adjust the view column name if necessary. 
 
-    
-    QString viewQuery = "SELECT definition FROM pg_views "
-      "WHERE schemaname = '" + temp.view_schema + "' AND "
-      "viewname = '" + temp.view_name + "'";
- 
-    // Maintain a cache of the above SQL.
-    QString viewDef;
-    if (!viewDefs.contains(viewQuery))
-    {
-      PGresult* r = PQexec(connection, (const char*)(viewQuery.utf8()));
-      if (PQntuples(r) > 0)
-        viewDef = PQgetvalue(r, 0, 0);
-      else
-        QgsDebugMsg("Failed to get view definition for " + temp.view_schema + "." + temp.view_name);
-      viewDefs[viewQuery] = viewDef;
-    }
-
-    viewDef = viewDefs.value(viewQuery);
-
     // Now pick the view definiton apart, looking for
     // temp.column_name to the left of an 'AS'.
 
-    // This regular expression needs more testing. Since the view
-    // definition comes from postgresql and has been 'standardised', we
-    // don't need to deal with everything that the user could put in a view
-    // definition. Does the regexp have to deal with the schema??
     if (!viewDef.isEmpty())
     {
+      // This regular expression needs more testing. Since the view
+      // definition comes from postgresql and has been 'standardised', we
+      // don't need to deal with everything that the user could put in a view
+      // definition. Does the regexp have to deal with the schema??
+
       QRegExp s(".* \"?" + QRegExp::escape(temp.table_name) +
                 "\"?\\.\"?" + QRegExp::escape(temp.column_name) +
                 "\"? AS \"?(\\w+)\"?,* .*");
@@ -1257,7 +1244,6 @@ void QgsPostgresProvider::findColumns(tableCols& cols)
       if (s.indexIn(viewDef) != -1)
       {
         temp.view_column_name = s.cap(1);
-        //std::cerr<<__FILE__<<__LINE__<<' '<<temp.view_column_name.toLocal8Bit().data()<<'\n';
       }
     }