libtracker-data: Check for already visited properties during flush

Due to TrackerResource insertion trying to avoid too frequent flushing,
we might end up with a single batch containing multiple single-valued
property delete+insert changes for the same resource/property. These
currently fail with "multiple values for single-valued property" errors
but that will be fixed in a followup commit.

If these got through, we would want to avoid telling SQLite about
these properties several times, e.g.:

  INSERT OR REPLACE INTO ... (ID, "nfo:fileSize", "nfo:fileSize")

Since what happens then is unspecified (SQLite chooses to honor the
first value and ignore the second).

To fix this, check the already visited properties when generating
the INSERT/UPDATE statement for single-valued properties in a class
table, and ensure we stick to the last given value.

This avoids having to prematurely flush just to keep these two
changes separate, and coalesces things the right way (i.e. we end
up with the good, last value).

1 files changed, 25 insertions, 5 deletions

diff --git a/src/libtracker-data/tracker-data-update.c b/src/libtracker-data/tracker-data-update.c
index cbd2fc46a..2103271b0 100644
--- a/src/libtracker-data/tracker-data-update.c
+++ b/src/libtracker-data/tracker-data-update.c
@@ -874,6 +874,8 @@ tracker_data_resource_buffer_flush (TrackerData                      *data,
 			}
 		} else {
 			GString *sql, *values_sql;
+			GHashTable *visited_properties;
+			gint n;
 
 			if (table->delete_row) {
 				/* remove row from class table */
@@ -917,19 +919,28 @@ tracker_data_resource_buffer_flush (TrackerData                      *data,
 				g_string_append (sql, " SET ");
 			}
 
-			for (i = 0; i < table->properties->len; i++) {
-				property = &g_array_index (table->properties, TrackerDataUpdateBufferProperty, i);
+			visited_properties = g_hash_table_new (g_str_hash, g_str_equal);
+
+			for (n = table->properties->len - 1; n >= 0; n--) {
+				property = &g_array_index (table->properties, TrackerDataUpdateBufferProperty, n);
+				if (g_hash_table_contains (visited_properties, property->name))
+					continue;
+
 				if (table->insert) {
 					g_string_append_printf (sql, ", \"%s\"", property->name);
 					g_string_append (values_sql, ", ?");
 				} else {
-					if (i > 0) {
+					if (n < (int) table->properties->len - 1) {
 						g_string_append (sql, ", ");
 					}
 					g_string_append_printf (sql, "\"%s\" = ?", property->name);
 				}
+
+				g_hash_table_add (visited_properties, (gpointer) property->name);
 			}
 
+			g_hash_table_unref (visited_properties);
+
 			if (table->insert) {
 				g_string_append (sql, ")");
 				g_string_append (values_sql, ")");
@@ -966,16 +977,25 @@ tracker_data_resource_buffer_flush (TrackerData                      *data,
 				param = 0;
 			}
 
-			for (i = 0; i < table->properties->len; i++) {
-				property = &g_array_index (table->properties, TrackerDataUpdateBufferProperty, i);
+			visited_properties = g_hash_table_new (g_str_hash, g_str_equal);
+
+			for (n = table->properties->len - 1; n >= 0; n--) {
+				property = &g_array_index (table->properties, TrackerDataUpdateBufferProperty, n);
+				if (g_hash_table_contains (visited_properties, property->name))
+					continue;
+
 				if (property->delete_value) {
 					/* just set value to NULL for single value properties */
 					tracker_db_statement_bind_null (stmt, param++);
 				} else {
 					statement_bind_gvalue (stmt, &param, &property->value);
 				}
+
+				g_hash_table_add (visited_properties, (gpointer) property->name);
 			}
 
+			g_hash_table_unref (visited_properties);
+
 			if (!table->insert) {
 				tracker_db_statement_bind_int (stmt, param++, resource->id);
 			}