[geary/wip/search-fixes: 21/29] Use a single RO transaction when removing matches from a search

[Michael Gratton <mjog src gnome org>]

commit 7f0f7d21c3716ca646a626f33d8852edc30d07b7
Author: Michael Gratton <mike vee net>
Date:   Mon Aug 5 17:58:22 2019 +1000

    Use a single RO transaction when removing matches from a search
    
    Make ImapDb.Account::strip_removal_conditions use a single RO txn and
    manually load flags from the message row when looking up email to filter
    out, to keep overhead as low as possible.

 src/engine/imap-db/imap-db-account.vala | 37 +++++++++++++++++++++------------
 1 file changed, 24 insertions(+), 13 deletions(-)
---
diff --git a/src/engine/imap-db/imap-db-account.vala b/src/engine/imap-db/imap-db-account.vala
index 44cc0894..d4ce7818 100644
--- a/src/engine/imap-db/imap-db-account.vala
+++ b/src/engine/imap-db/imap-db-account.vala
@@ -676,23 +676,34 @@ private class Geary.ImapDB.Account : BaseObject {
     // given removal conditions
     private async void strip_removal_conditions(ImapDB.SearchQuery query,
                                                 Gee.Collection<EmailIdentifier> matches,
-                                                Gee.Map<Geary.NamedFlag, bool> conditions,
-                                                GLib.Cancellable? cancellable = null) {
+                                                Gee.Map<Geary.NamedFlag,bool> conditions,
+                                                GLib.Cancellable? cancellable = null)
+        throws GLib.Error {
         Email.Field required_fields = Geary.Email.Field.FLAGS;
         Gee.Iterator<EmailIdentifier> iter = matches.iterator();
-        while (iter.next()) {
-            try {
-                ImapDB.EmailIdentifier id = iter.get();
-                Geary.Email email = yield fetch_email_async(id, required_fields, cancellable);
-                foreach (Geary.NamedFlag flag in conditions.keys)
-                    if (email.email_flags.contains(flag) == conditions.get(flag)) {
+
+        yield db.exec_transaction_async(RO, (cx) => {
+                while (iter.next()) {
+                    ImapDB.EmailIdentifier id = iter.get();
+                    MessageRow row = Geary.ImapDB.Folder.do_fetch_message_row(
+                        cx, id.message_id, required_fields, null, cancellable
+                    );
+                    Geary.EmailFlags? flags = row.get_generic_email_flags();
+                    if (flags != null) {
+                        foreach (Gee.Map.Entry<NamedFlag,bool> condition
+                                 in conditions.entries) {
+                            if (flags.contains(condition.key) == condition.value) {
+                                iter.remove();
+                                break;
+                            }
+                        }
+                    } else {
                         iter.remove();
-                        break;
                     }
-            } catch (Error e) {
-                debug("Error fetching email: %s", e.message);
-            }
-        }
+                }
+                return Db.TransactionOutcome.DONE;
+            }, cancellable
+        );
     }
 
     // Strip out from the given collection of matching ids and results