Optimize FINDCSN case

diff --git a/servers/slapd/overlays/syncprov.c b/servers/slapd/overlays/syncprov.c
index 8ff375453f9c2eb9c4412126ae9a09a11271cb52..a78cfab33f8679ab86074082535d68156a542958 100644 (file)
--- a/servers/slapd/overlays/syncprov.c
+++ b/servers/slapd/overlays/syncprov.c
@@ -447,8 +447,8 @@ syncprov_findbase( Operation *op, fbase_cookie *fc )
  * was not checkpointed at the previous shutdown.
  *
  * 2: when the current contextCSN is known and we have a sync cookie, we search
- * for one entry with CSN <= the cookie CSN. (Used to search for =.) If an
- * entry is found, the cookie CSN is valid, otherwise it is stale.
+ * for one entry with CSN = the cookie CSN. If not found, try <= cookie CSN.
+ * If an entry is found, the cookie CSN is valid, otherwise it is stale.
  *
  * 3: during a refresh phase, we search for all entries with CSN <= the cookie
  * CSN, and generate Present records for them. We always collect this result
@@ -555,6 +555,7 @@ syncprov_findcsn( Operation *op, int mode )
        int i, rc = LDAP_SUCCESS;
        fpres_cookie pcookie;
        sync_control *srs = NULL;
+       int findcsn_retry = 1;
 
        if ( mode != FIND_MAXCSN ) {
                srs = op->o_controls[slap_cids.sc_LDAPsync];
@@ -579,6 +580,7 @@ syncprov_findcsn( Operation *op, int mode )
        fop.ors_filter = &cf;
        fop.ors_filterstr.bv_val = buf;
 
+again:
        switch( mode ) {
        case FIND_MAXCSN:
                cf.f_choice = LDAP_FILTER_GE;
@@ -595,10 +597,18 @@ syncprov_findcsn( Operation *op, int mode )
                maxcsn.bv_len = si->si_ctxcsn.bv_len;
                break;
        case FIND_CSN:
-               cf.f_choice = LDAP_FILTER_LE;
+               /* Look for exact match the first time */
+               if ( findcsn_retry ) {
+                       cf.f_choice = LDAP_FILTER_EQUALITY;
+                       fop.ors_filterstr.bv_len = sprintf( buf, "(entryCSN=%s)",
+                               cf.f_av_value.bv_val );
+               /* On retry, look for <= */
+               } else {
+                       cf.f_choice = LDAP_FILTER_LE;
+                       fop.ors_filterstr.bv_len = sprintf( buf, "(entryCSN<=%s)",
+                               cf.f_av_value.bv_val );
+               }
                cf.f_av_value = srs->sr_state.ctxcsn;
-               fop.ors_filterstr.bv_len = sprintf( buf, "(entryCSN<=%s)",
-                       cf.f_av_value.bv_val );
                fop.ors_attrsonly = 1;
                fop.ors_attrs = slap_anlist_no_attrs;
                fop.ors_slimit = 1;
@@ -646,7 +656,14 @@ syncprov_findcsn( Operation *op, int mode )
                break;
        case FIND_CSN:
                /* If matching CSN was not found, invalidate the context. */
-               if ( !cb.sc_private ) rc = LDAP_NO_SUCH_OBJECT;
+               if ( !cb.sc_private ) {
+                       /* If we didn't find an exact match, then try for <= */
+                       if ( findcsn_retry ) {
+                               findcsn_retry = 0;
+                               goto again;
+                       }
+                       rc = LDAP_NO_SUCH_OBJECT;
+               }
                break;
        case FIND_PRESENT:
                op->o_tmpfree( pcookie.uuids, op->o_tmpmemctx );