Only upsert once for each distinct character group (#714)

* Only upsert once for each distinct character group

* .Q.fu optimisation.

Co-authored-by: Ryan Cheale <ryan.cheale@dataintellect.com>

* Reduced changes to upserttopartition

---------

Co-authored-by: Ryan Cheale <ryan.cheale@dataintellect.com>

Author: j-muldoon

code/processes/wdb.q

@@ -144,7 +144,8 @@ upserttopartition:{[dir;tablename;tabdata;pt;expttype;expt;writedownmode]
                   ` sv .Q.par[dir;pt;tablename],(`$"_"^.Q.an .Q.an?"_" sv string `TORQNULLSYMBOL^ ensuresymlist[expt]),`];
     .lg.o[`save;"saving ",(string tablename)," data to partition ",string directory];
     /- selecting rows of table with matching partition
-    r:?[tabdata;$[writedownmode in `partbyenum`partbyfirstchar;enlist(in;first expttype;expt);{(x;y;(),z)}[in;;]'[expttype;expt]];0b;()];
+    r:?[tabdata;$[writedownmode in `partbyenum`partbyfirstchar;enlist(in;first expttype;enlist expt);
+        {(x;y;(),z)}[in;;]'[expttype;expt]];0b;()];
     /- upsert selected data matched on partition to specific directory
     .[upsert;(directory;r);{[e] .lg.e[`savetablesbypart;"Failed to save table to disk : ",e];'e}];
     .lg.o[`track;"appending details to partsizes"];
@@ -168,6 +169,8 @@ savetablesbypart:{[dir;pt;forcesave;tablename;writedownmode]
         if[writedownmode~`partbyenum;.merge.checkenumerabletype[tablename;extrapartitiontype]];
         /- get list of distinct combinations for partition directories
         extrapartitions:.merge.getextrapartitions[tablename;extrapartitiontype];
+        if[writedownmode~`partbyfirstchar; 
+            extrapartitions:value extrapartitions group .Q.fu[{first each string x}; extrapartitions:raze extrapartitions]];
         /- enumerate data to be upserted
         enumdata:.Q.en[hdbsettings[`hdbdir];0!.save.manipulate[tablename;`. tablename]];
         .lg.o[`save;"enumerated ",(string tablename)," table"];