PostGIS backend: translate insensitive equality comparison as Postgre SQL lower(foo::text) = lower('bar').

Fixes a performance issue dating from 7.0

The wfs_filter_postgis.map wfs_filter_postgis_property_is_equal_case_insensitive
test case exercices this code path.

Author: rouault

mappostgis.c

@@ -4036,6 +4036,8 @@ int msPostGISLayerTranslateFilter(layerObj *layer, expressionObj *filter, char *
     msFree(snippet);
     msFree(stresc);
   } else if(filter->type == MS_EXPRESSION) {
+    int ieq_expected = MS_FALSE;
+
     if(msPostGISParseData(layer) != MS_SUCCESS) return MS_FAILURE;
 
     if(layer->debug >= 2) msDebug("msPostGISLayerTranslateFilter. String: %s.\n", filter->string);
@@ -4050,7 +4052,9 @@ int msPostGISLayerTranslateFilter(layerObj *layer, expressionObj *filter, char *
       */
       if(node->token == MS_TOKEN_BINDING_TIME) {
         bindingToken = node->token;
-      } else if(node->token == MS_TOKEN_COMPARISON_EQ || node->token == MS_TOKEN_COMPARISON_NE ||
+      } else if(node->token == MS_TOKEN_COMPARISON_EQ ||
+         node->token == MS_TOKEN_COMPARISON_IEQ ||
+         node->token == MS_TOKEN_COMPARISON_NE ||
          node->token == MS_TOKEN_COMPARISON_GT || node->token == MS_TOKEN_COMPARISON_GE ||
          node->token == MS_TOKEN_COMPARISON_LT || node->token == MS_TOKEN_COMPARISON_LE ||
          node->token == MS_TOKEN_COMPARISON_IN) {
@@ -4101,7 +4105,10 @@ int msPostGISLayerTranslateFilter(layerObj *layer, expressionObj *filter, char *
 
             msFreeCharArray(strings, nstrings);
           } else {
-            strtmpl = "'%s'";
+            if(comparisonToken == MS_TOKEN_COMPARISON_IEQ)
+                strtmpl = "lower('%s')";
+            else
+                strtmpl = "'%s'";
             stresc = msPostGISEscapeSQLParam(layer, node->tokenval.strval);
             snippet = (char *) msSmallMalloc(strlen(strtmpl) + strlen(stresc));
             sprintf(snippet, strtmpl, stresc);
@@ -4149,7 +4156,11 @@ int msPostGISLayerTranslateFilter(layerObj *layer, expressionObj *filter, char *
         case MS_TOKEN_BINDING_DOUBLE:
         case MS_TOKEN_BINDING_INTEGER:
         case MS_TOKEN_BINDING_STRING:
-          if(node->token == MS_TOKEN_BINDING_STRING || node->next->token == MS_TOKEN_COMPARISON_RE || node->next->token == MS_TOKEN_COMPARISON_IRE)
+          if (node->token == MS_TOKEN_BINDING_STRING && node->next->token == MS_TOKEN_COMPARISON_IEQ ) {
+            strtmpl = "lower(%s::text)";
+            ieq_expected = MS_TRUE;
+          }
+          else if(node->token == MS_TOKEN_BINDING_STRING || node->next->token == MS_TOKEN_COMPARISON_RE || node->next->token == MS_TOKEN_COMPARISON_IRE)
             strtmpl = "%s::text"; /* explicit cast necessary for certain operators */
           else
             strtmpl = "%s";
@@ -4195,8 +4206,19 @@ int msPostGISLayerTranslateFilter(layerObj *layer, expressionObj *filter, char *
           native_string = msStringConcatenate(native_string, msExpressionTokenToString(node->token));
           break;
 
-	/* unsupported tokens */ 
 	case MS_TOKEN_COMPARISON_IEQ:
+            if( ieq_expected )
+            {
+                native_string = msStringConcatenate(native_string, "=");
+                ieq_expected = MS_FALSE;
+            }
+            else
+            {
+                goto cleanup;
+            }
+            break;
+
+	/* unsupported tokens */
         case MS_TOKEN_COMPARISON_BEYOND:
 	case MS_TOKEN_FUNCTION_TOSTRING:
 	case MS_TOKEN_FUNCTION_ROUND: