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+From: david@tethera.net\r
+To: notmuch@notmuchmail.org\r
+Subject: [Patch v2 17/17] tag-util: optimization of tag application\r
+Date: Sat, 24 Nov 2012 17:20:17 -0400\r
+Message-Id: <1353792017-31459-18-git-send-email-david@tethera.net>\r
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+Cc: David Bremner <bremner@debian.org>\r
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+\r
+From: David Bremner <bremner@debian.org>\r
+\r
+The idea is not to bother with restore operations if they don't change\r
+the set of tags. This is actually a relatively common case.\r
+\r
+In order to avoid fancy datastructures, this method is quadratic in\r
+the number of tags; at least on my mail database this doesn't seem to\r
+be a big problem.\r
+---\r
+ notmuch-tag.c | 2 +-\r
+ tag-util.c | 59 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++\r
+ 2 files changed, 60 insertions(+), 1 deletion(-)\r
+\r
+diff --git a/notmuch-tag.c b/notmuch-tag.c\r
+index 8a8af0b..e4fca67 100644\r
+--- a/notmuch-tag.c\r
++++ b/notmuch-tag.c\r
+@@ -140,7 +140,7 @@ tag_query (void *ctx, notmuch_database_t *notmuch, const char *query_string,\r
+ notmuch_messages_valid (messages) && ! interrupted;\r
+ notmuch_messages_move_to_next (messages)) {\r
+ message = notmuch_messages_get (messages);\r
+- tag_op_list_apply (message, tag_ops, flags);\r
++ tag_op_list_apply (message, tag_ops, flags | TAG_FLAG_PRE_OPTIMIZED);\r
+ notmuch_message_destroy (message);\r
+ }\r
+ \r
+diff --git a/tag-util.c b/tag-util.c\r
+index 287cc67..2bb8355 100644\r
+--- a/tag-util.c\r
++++ b/tag-util.c\r
+@@ -111,6 +111,62 @@ message_error (notmuch_message_t *message,\r
+ fprintf (stderr, "Status: %s\n", notmuch_status_to_string (status));\r
+ }\r
+ \r
++static int\r
++makes_changes (notmuch_message_t *message,\r
++ tag_op_list_t *list,\r
++ tag_op_flag_t flags)\r
++{\r
++\r
++ int i;\r
++\r
++ notmuch_tags_t *tags;\r
++ notmuch_bool_t changes = FALSE;\r
++\r
++ /* First, do we delete an existing tag? */\r
++ changes = FALSE;\r
++ for (tags = notmuch_message_get_tags (message);\r
++ ! changes && notmuch_tags_valid (tags);\r
++ notmuch_tags_move_to_next (tags)) {\r
++ const char *cur_tag = notmuch_tags_get (tags);\r
++ int last_op = (flags & TAG_FLAG_REMOVE_ALL) ? -1 : 0;\r
++\r
++ for (i = 0; i < list->count; i++) {\r
++ if (strcmp (cur_tag, list->ops[i].tag) == 0) {\r
++ last_op = list->ops[i].remove ? -1 : 1;\r
++ }\r
++ }\r
++\r
++ changes = (last_op == -1);\r
++ }\r
++ notmuch_tags_destroy (tags);\r
++\r
++ if (changes)\r
++ return TRUE;\r
++\r
++ /* Now check for adding new tags */\r
++ for (i = 0; i < list->count; i++) {\r
++ notmuch_bool_t exists = FALSE;\r
++\r
++ for (tags = notmuch_message_get_tags (message);\r
++ notmuch_tags_valid (tags);\r
++ notmuch_tags_move_to_next (tags)) {\r
++ const char *cur_tag = notmuch_tags_get (tags);\r
++ if (strcmp (cur_tag, list->ops[i].tag) == 0) {\r
++ exists = TRUE;\r
++ break;\r
++ }\r
++ }\r
++ notmuch_tags_destroy (tags);\r
++\r
++ /* the following test is conservative, it's ok to think we\r
++ * make changes when we don't */\r
++ if ( ! exists && ! list->ops[i].remove )\r
++ return TRUE;\r
++ }\r
++ return FALSE;\r
++\r
++}\r
++\r
+ notmuch_status_t\r
+ tag_op_list_apply (notmuch_message_t *message,\r
+ tag_op_list_t *list,\r
+@@ -121,6 +177,9 @@ tag_op_list_apply (notmuch_message_t *message,\r
+ notmuch_status_t status = 0;\r
+ tag_operation_t *tag_ops = list->ops;\r
+ \r
++ if (! (flags & TAG_FLAG_PRE_OPTIMIZED) && ! makes_changes (message, list, flags))\r
++ return NOTMUCH_STATUS_SUCCESS;\r
++\r
+ status = notmuch_message_freeze (message);\r
+ if (status) {\r
+ message_error (message, status, "freezing message");\r
+-- \r
+1.7.10.4\r
+\r