xap_helper: avoid temporary std::set in thread fp

Instead of creating a temporary std::set to store THREADIDs,
just inject the Xapian::Query::OP_OR operations directly into
the query we return.

Unlike notmuch(1), we can do this without risking redundant
query ops from repeated THREADIDs since use since we use a
column instead of a term for THREADID.  Column use allowed
us to use .set_collapse_key to deduplicate the intermediate
mset, already.

diff --git a/lib/PublicInbox/xh_thread_fp.h b/lib/PublicInbox/xh_thread_fp.h
index 2c88401c8dfc3154b20b84bf3e5e3b55fffca3f6..27b5cfcb58e842af6cd5f800cd4800de26da8f89 100644 (file)
--- a/lib/PublicInbox/xh_thread_fp.h
+++ b/lib/PublicInbox/xh_thread_fp.h
@@ -10,13 +10,17 @@ public:
        Xapian::Query operator()(const std::string &str);
 };
 
-static enum exc_iter xpand_col_iter(std::set<std::string> &vals,
+static enum exc_iter xpand_col_iter(Xapian::Query *xqry,
                                        Xapian::MSetIterator *i,
                                        unsigned column)
 {
        try {
                Xapian::Document doc = i->get_document();
-               vals.insert(doc.get_value(column));
+               std::string val = doc.get_value(column);
+               *xqry = Xapian::Query(Xapian::Query::OP_OR, *xqry,
+                               Xapian::Query(
+                                       Xapian::Query::OP_VALUE_RANGE,
+                                       column, val, val));
        } catch (const Xapian::DatabaseModifiedError &e) {
                cur_srch->db->reopen();
                return ITER_RETRY;
@@ -29,9 +33,7 @@ static enum exc_iter xpand_col_iter(std::set<std::string> &vals,
 static Xapian::Query qry_xpand_col(Xapian::Query qry, unsigned column)
 {
        Xapian::Query xqry = Xapian::Query::MatchNothing;
-
        Xapian::Enquire enq(*cur_srch->db);
-       std::set<std::string> vals; // serialised Xapian column
 
        enq.set_weighting_scheme(Xapian::BoolWeight());
        enq.set_query(qry);
@@ -41,19 +43,12 @@ static Xapian::Query qry_xpand_col(Xapian::Query qry, unsigned column)
 
        for (Xapian::MSetIterator i = mset.begin(); i != mset.end(); i++)  {
                for (int t = 10; t > 0; --t)
-                       switch (xpand_col_iter(vals, &i, column)) {
+                       switch (xpand_col_iter(&xqry, &i, column)) {
                        case ITER_OK: t = 0; break; // leave inner loop
                        case ITER_RETRY: break; // continue for-loop
                        case ITER_ABORT: return xqry; // impossible
                        }
        }
-
-       std::set<std::string>::const_iterator tid;
-       for (tid = vals.begin(); tid != vals.end(); tid++)
-               xqry = Xapian::Query(Xapian::Query::OP_OR, xqry,
-                               Xapian::Query(
-                                       Xapian::Query::OP_VALUE_RANGE,
-                                       column, *tid, *tid));
        return xqry;
 }