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

[Carlos Garnacho <carlosg src gnome org>]

commit 057c03d4025516f526942db52c797b09a0063b59
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 811b34b22..9ce67f3fd 100644
--- a/src/libtracker-data/tracker-sparql.c
+++ b/src/libtracker-data/tracker-sparql.c
@@ -2828,12 +2828,32 @@ 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 ')' ) )+ 
| '*' )
@@ -2852,6 +2872,8 @@ 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;
@@ -2867,35 +2889,45 @@ 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) {
+                               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;
@@ -2907,7 +2939,7 @@ 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);
@@ -2941,7 +2973,6 @@ 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;
@@ -2955,7 +2986,7 @@ 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;
 
@@ -2974,12 +3005,17 @@ 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);