[tracker/wip/carlosg/serialize-api: 7/13] libtracker-data: Forward annotated column types on SELECT queries

[Carlos Garnacho <carlosg src gnome org>]

commit dcbbfffb8a1839bab2ded37a86e317d09efdee1c
Author: Carlos Garnacho <carlosg gnome org>
Date:   Sun Jan 30 15:39:46 2022 +0100

    libtracker-data: Forward annotated column types on SELECT queries
    
    Forward this additional information in the query itself, as extra columns
    after the user visible ones. We already have ":type" suffixed subvariables
    for the places where we cannot infer that from the query being parsed,
    prefer these to the TrackerPropertyType found out at parse time, as that
    will contain the real type for the given column at the current row.

 src/libtracker-data/tracker-sparql.c | 56 +++++++++++++++++++++++++++++-------
 1 file changed, 46 insertions(+), 10 deletions(-)
---
diff --git a/src/libtracker-data/tracker-sparql.c b/src/libtracker-data/tracker-sparql.c
index 93c33f40e..857102e93 100644
--- a/src/libtracker-data/tracker-sparql.c
+++ b/src/libtracker-data/tracker-sparql.c
@@ -2827,12 +2827,32 @@ handle_as (TrackerSparql        *sparql,
        return TRUE;
 }
 
+static void
+handle_value_type_column (TrackerSparql        *sparql,
+                          TrackerPropertyType   prop_type,
+                          TrackerVariable      *var)
+{
+       TrackerVariable *type_var = NULL;
+
+       if (var)
+               type_var = lookup_subvariable (sparql, var, "type");
+
+       if (type_var) {
+               /* If a $var:type variable exists for this variable, use that */
+               _append_string_printf (sparql, ", %s ",
+                                      tracker_variable_get_sql_expression (type_var));
+       } else {
+               _append_string_printf (sparql, ", %d ", prop_type);
+       }
+}
+
 static gboolean
 translate_SelectClause (TrackerSparql  *sparql,
                         GError        **error)
 {
        TrackerSelectContext *select_context;
        TrackerStringBuilder *str, *old;
+       TrackerStringBuilder *vars, *types;
        gboolean first = TRUE;
 
        /* SelectClause ::= 'SELECT' ( 'DISTINCT' | 'REDUCED' )? ( ( Var | ( '(' Expression 'AS' Var ')' ) )+ 
| '*' )
@@ -2851,6 +2871,8 @@ translate_SelectClause (TrackerSparql  *sparql,
        }
 
        select_context = TRACKER_SELECT_CONTEXT (sparql->current_state->select_context);
+       vars = _append_placeholder (sparql);
+       types = _append_placeholder (sparql);
 
        if (_accept (sparql, RULE_TYPE_LITERAL, LITERAL_GLOB)) {
                TrackerVariable *var;
@@ -2866,38 +2888,48 @@ translate_SelectClause (TrackerSparql  *sparql,
                g_hash_table_iter_init (&iter, select_context->variables);
 
                while (g_hash_table_iter_next (&iter, NULL, (gpointer *) &var)) {
+                       TrackerPropertyType prop_type;
+
                        /* Skip our own internal variables */
                        if (strchr (var->name, ':'))
                                continue;
 
+                       old = tracker_sparql_swap_builder (sparql, vars);
+
                        if (!first)
                                _append_string (sparql, ", ");
 
                        str = _append_placeholder (sparql);
-                       old = tracker_sparql_swap_builder (sparql, str);
+                       tracker_sparql_swap_builder (sparql, str);
+                       prop_type = TRACKER_BINDING (tracker_variable_get_sample_binding (var))->data_type;
 
                        _append_string_printf (sparql, "%s ",
                                               tracker_variable_get_sql_expression (var));
 
                        if (sparql->current_state->select_context == sparql->context) {
-                               TrackerPropertyType prop_type;
-
-                               prop_type = TRACKER_BINDING (tracker_variable_get_sample_binding 
(var))->data_type;
                                convert_expression_to_string (sparql, prop_type);
                        }
 
                        if (sparql->current_state->select_context == sparql->context)
                                _append_string_printf (sparql, "AS \"%s\" ", var->name);
 
+                       if (sparql->current_state->select_context == sparql->context) {
+                               tracker_sparql_swap_builder (sparql, types);
+                               handle_value_type_column (sparql, prop_type, var);
+                       }
+
                        tracker_sparql_swap_builder (sparql, old);
+
                        first = FALSE;
                        select_context->n_columns++;
                }
        } else {
                do {
-                       TrackerVariable *var;
+                       TrackerVariable *var = NULL;
                        TrackerPropertyType prop_type;
 
+                       old = tracker_sparql_swap_builder (sparql, vars);
+
                        if (_check_in_rule (sparql, NAMED_RULE_Var)) {
                                gchar *name;
                                gboolean found;
@@ -2909,7 +2941,7 @@ translate_SelectClause (TrackerSparql  *sparql,
                                name = _dup_last_string (sparql);
 
                                str = _append_placeholder (sparql);
-                               old = tracker_sparql_swap_builder (sparql, str);
+                               tracker_sparql_swap_builder (sparql, str);
 
                                found = tracker_context_lookup_variable_by_name 
(sparql->current_state->context,
                                                                                 name);
@@ -2940,7 +2972,6 @@ translate_SelectClause (TrackerSparql  *sparql,
                                        tracker_sparql_add_select_var (sparql, name, prop_type);
                                }
 
-                               tracker_sparql_swap_builder (sparql, old);
                                g_free (name);
                        } else {
                                gboolean parens = FALSE;
@@ -2954,7 +2985,7 @@ translate_SelectClause (TrackerSparql  *sparql,
                                        _append_string (sparql, ", ");
 
                                str = _append_placeholder (sparql);
-                               old = tracker_sparql_swap_builder (sparql, str);
+                               tracker_sparql_swap_builder (sparql, str);
                                _call_rule (sparql, NAMED_RULE_Expression, error);
                                prop_type = sparql->current_state->expression_type;
 
@@ -2973,12 +3004,17 @@ translate_SelectClause (TrackerSparql  *sparql,
                                        tracker_sparql_add_select_var (sparql, "", prop_type);
                                }
 
-                               tracker_sparql_swap_builder (sparql, old);
-
                                if (parens)
                                        _expect (sparql, RULE_TYPE_LITERAL, LITERAL_CLOSE_PARENS);
                        }
 
+                       if (sparql->current_state->select_context == sparql->context) {
+                               tracker_sparql_swap_builder (sparql, types);
+                               handle_value_type_column (sparql, prop_type, var);
+                       }
+
+                       tracker_sparql_swap_builder (sparql, old);
+
                        first = FALSE;
                        select_context->n_columns++;
                } while (TRUE);