MWL#17: Table elimination

- Move eliminate_tables() to before constant table detection. 
- First code for benchmark

sql-bench/test-table-elimination.sh:
  MWL#17: Table elimination
  - sql-bench "Benchmark", incomplete
sql/sql_select.cc:
  MWL#17: Table elimination
  - Move eliminate_tables() to before constant table detection, this will allow
    to spare const table reads (at a cost of not being able to take advantage of 
    tables that are constant because they have no records, but this case is of 
    lesser importance)

sql-bench/test-table-elimination.sh

+#!@PERL@
+# Test of table elimination feature
+
+use Cwd;
+use DBI;
+use Getopt::Long;
+use Benchmark;
+
+$opt_loop_count=100000;
+$opt_medium_loop_count=10000;
+$opt_small_loop_count=100;
+
+$pwd = cwd(); $pwd = "." if ($pwd eq '');
+require "$pwd/bench-init.pl" || die "Can't read Configuration file: $!\n";
+
+if ($opt_small_test)
+{
+  $opt_loop_count/=10;
+  $opt_medium_loop_count/=10;
+  $opt_small_loop_count/=10;
+}
+
+print "Testing table elimination feature\n";
+print "The test table has $opt_loop_count rows.\n\n";
+
+# A query to get the recent versions of all attributes:
+$select_current_full_facts="
+  select 
+    F.id, A1.attr1, A2.attr2
+  from 
+    elim_facts F 
+    left join elim_attr1 A1 on A1.id=F.id
+    left join elim_attr2 A2 on A2.id=F.id and 
+                               A2.fromdate=(select MAX(fromdate) from
+                                            elim_attr2 where id=A2.id);
+";
+$select_current_full_facts="
+  select 
+    F.id, A1.attr1, A2.attr2
+  from 
+    elim_facts F 
+    left join elim_attr1 A1 on A1.id=F.id
+    left join elim_attr2 A2 on A2.id=F.id and 
+                               A2.fromdate=(select MAX(fromdate) from
+                                            elim_attr2 where id=F.id);
+";
+# TODO: same as above but for some given date also? 
+# TODO: 
+
+
+####
+####  Connect and start timeing
+####
+
+$dbh = $server->connect();
+$start_time=new Benchmark;
+
+####
+#### Create needed tables
+####
+
+goto select_test if ($opt_skip_create);
+
+print "Creating tables\n";
+$dbh->do("drop table elim_facts" . $server->{'drop_attr'});
+$dbh->do("drop table elim_attr1" . $server->{'drop_attr'});
+$dbh->do("drop table elim_attr2" . $server->{'drop_attr'});
+
+# The facts table
+do_many($dbh,$server->create("elim_facts",
+			     ["id integer"],
+			     ["primary key (id)"]));
+
+# Attribute1, non-versioned
+do_many($dbh,$server->create("elim_attr1",
+			     ["id integer",
+                              "attr1 integer"],
+			     ["primary key (id)",
+                              "key (attr1)"]));
+
+# Attribute1, time-versioned
+do_many($dbh,$server->create("elim_attr2",
+			     ["id integer",
+                              "attr2 integer",
+                              "fromdate date"],
+			     ["primary key (id, fromdate)",
+                              "key (attr2,fromdate)"]));
+
+#NOTE: ignoring: if ($limits->{'views'})
+$dbh->do("drop view elim_current_facts");
+$dbh->do("create view elim_current_facts as $select_current_full_facts");
+
+if ($opt_lock_tables)
+{
+  do_query($dbh,"LOCK TABLES elim_facts, elim_attr1, elim_attr2 WRITE");
+}
+
+if ($opt_fast && defined($server->{vacuum}))
+{
+  $server->vacuum(1,\$dbh);
+}
+
+####
+#### Fill the facts table
+####
+$n_facts= $opt_loop_count;
+
+if ($opt_fast && $server->{transactions})
+{
+  $dbh->{AutoCommit} = 0;
+}
+
+print "Inserting $n_facts rows into facts table\n";
+$loop_time=new Benchmark;
+
+$query="insert into elim_facts values (";
+for ($id=0; $id < $n_facts ; $id++)
+{
+  do_query($dbh,"$query $id)");
+}
+
+if ($opt_fast && $server->{transactions})
+{
+  $dbh->commit;
+  $dbh->{AutoCommit} = 1;
+}
+
+$end_time=new Benchmark;
+print "Time to insert ($n_facts): " .
+    timestr(timediff($end_time, $loop_time),"all") . "\n\n";
+
+####
+#### Fill attr1 table
+####
+if ($opt_fast && $server->{transactions})
+{
+  $dbh->{AutoCommit} = 0;
+}
+
+print "Inserting $n_facts rows into attr1 table\n";
+$loop_time=new Benchmark;
+
+$query="insert into elim_attr1 values (";
+for ($id=0; $id < $n_facts ; $id++)
+{
+  $attr1= ceil(rand($n_facts));
+  do_query($dbh,"$query $id, $attr1)");
+}
+
+if ($opt_fast && $server->{transactions})
+{
+  $dbh->commit;
+  $dbh->{AutoCommit} = 1;
+}
+
+$end_time=new Benchmark;
+print "Time to insert ($n_facts): " .
+    timestr(timediff($end_time, $loop_time),"all") . "\n\n";
+
+####
+#### Fill attr2 table
+####
+if ($opt_fast && $server->{transactions})
+{
+  $dbh->{AutoCommit} = 0;
+}
+
+print "Inserting $n_facts rows into attr2 table\n";
+$loop_time=new Benchmark;
+
+for ($id=0; $id < $n_facts ; $id++)
+{
+  # Two values for each $id - current one and obsolete one.
+  $attr1= ceil(rand($n_facts));
+  $query="insert into elim_attr2 values ($id, $attr1, now())";
+  do_query($dbh,$query);
+  $query="insert into elim_attr2 values ($id, $attr1, '2009-01-01')";
+  do_query($dbh,$query);
+}
+
+if ($opt_fast && $server->{transactions})
+{
+  $dbh->commit;
+  $dbh->{AutoCommit} = 1;
+}
+
+$end_time=new Benchmark;
+print "Time to insert ($n_facts): " .
+    timestr(timediff($end_time, $loop_time),"all") . "\n\n";
+
+####
+####  Finalize the database population
+####
+
+if ($opt_lock_tables)
+{
+  do_query($dbh,"UNLOCK TABLES");
+}
+
+if ($opt_fast && defined($server->{vacuum}))
+{
+  $server->vacuum(0,\$dbh,["elim_facts", "elim_attr1", "elim_attr2"]);
+}
+
+if ($opt_lock_tables)
+{
+  do_query($dbh,"LOCK TABLES elim_facts, elim_attr1, elim_attr2 WRITE");
+}
+
+####
+#### Do some selects on the table
+####
+
+select_test:
+
+#
+# The selects will be:
+#   - N pk-lookups with all attributes 
+#   - pk-attribute-based lookup
+#   - latest-attribute value based lookup.
+
+
+###
+### Bare facts select:
+###
+print "testing bare facts facts table\n";
+$loop_time=new Benchmark;
+$rows=0;
+for ($i=0 ; $i < $opt_medium_loop_count ; $i++)
+{
+  $val= ceil(rand($n_facts));
+  $rows+=fetch_all_rows($dbh,"select * from elim_facts where id=$val");
+}
+$count=$i;
+
+$end_time=new Benchmark;
+print "time for select_bare_facts ($count:$rows): " .
+    timestr(timediff($end_time, $loop_time),"all") . "\n";
+
+
+###
+### Full facts select, no elimination:
+###
+print "testing full facts facts table\n";
+$loop_time=new Benchmark;
+$rows=0;
+for ($i=0 ; $i < $opt_medium_loop_count ; $i++)
+{
+  $val= rand($n_facts);
+  $rows+=fetch_all_rows($dbh,"select * from elim_current_facts where id=$val");
+}
+$count=$i;
+
+$end_time=new Benchmark;
+print "time for select_two_attributes ($count:$rows): " .
+    timestr(timediff($end_time, $loop_time),"all") . "\n";
+
+###
+### Now with elimination: select only only one fact
+###
+print "testing selection of one attribute\n";
+$loop_time=new Benchmark;
+$rows=0;
+for ($i=0 ; $i < $opt_medium_loop_count ; $i++)
+{
+  $val= rand($n_facts);
+  $rows+=fetch_all_rows($dbh,"select id, attr1 from elim_current_facts where id=$val");
+}
+$count=$i;
+
+$end_time=new Benchmark;
+print "time for select_one_attribute ($count:$rows): " .
+    timestr(timediff($end_time, $loop_time),"all") . "\n";
+
+###
+### Now with elimination: select only only one fact
+###
+print "testing selection of one attribute\n";
+$loop_time=new Benchmark;
+$rows=0;
+for ($i=0 ; $i < $opt_medium_loop_count ; $i++)
+{
+  $val= rand($n_facts);
+  $rows+=fetch_all_rows($dbh,"select id, attr2 from elim_current_facts where id=$val");
+}
+$count=$i;
+
+$end_time=new Benchmark;
+print "time for select_one_attribute ($count:$rows): " .
+    timestr(timediff($end_time, $loop_time),"all") . "\n";
+
+
+###
+### TODO...
+###
+
+;
+
+####
+#### End of benchmark
+####
+
+if ($opt_lock_tables)
+{
+  do_query($dbh,"UNLOCK TABLES");
+}
+if (!$opt_skip_delete)
+{
+  do_query($dbh,"drop table elim_facts, elim_attr1, elim_attr2" . $server->{'drop_attr'});
+}
+
+if ($opt_fast && defined($server->{vacuum}))
+{
+  $server->vacuum(0,\$dbh);
+}
+
+$dbh->disconnect;				# close connection
+
+end_benchmark($start_time);
+

sql/sql_select.cc

@@ -2959,22 +2959,28 @@ make_join_statistics(JOIN *join, TABLE_LIST *tables_arg, COND *conds,
 
   /* Read tables with 0 or 1 rows (system tables) */
   join->const_table_map= 0;
+  
+  eliminate_tables(join, &const_count, &found_const_table_map);
+  join->const_table_map= found_const_table_map;
 
   for (POSITION *p_pos=join->positions, *p_end=p_pos+const_count;
        p_pos < p_end ;
        p_pos++)
   {
-    int tmp;
     s= p_pos->table;
-    s->type=JT_SYSTEM;
-    join->const_table_map|=s->table->map;
-    if ((tmp=join_read_const_table(s, p_pos)))
+    if (! (s->table->map & join->eliminated_tables))
     {
-      if (tmp > 0)
-	goto error;		// Fatal error
+      int tmp;
+      s->type=JT_SYSTEM;
+      join->const_table_map|=s->table->map;
+      if ((tmp=join_read_const_table(s, p_pos)))
+      {
+        if (tmp > 0)
+          goto error;		// Fatal error
+      }
+      else
+        found_const_table_map|= s->table->map;
     }
-    else
-      found_const_table_map|= s->table->map;
   }
 
   /* loop until no more const tables are found */
@@ -2999,7 +3005,8 @@ make_join_statistics(JOIN *join, TABLE_LIST *tables_arg, COND *conds,
         substitution of a const table the key value happens to be null
         then we can state that there are no matches for this equi-join.
       */  
-      if ((keyuse= s->keyuse) && *s->on_expr_ref && !s->embedding_map)
+      if ((keyuse= s->keyuse) && *s->on_expr_ref && !s->embedding_map &&
+         !(table->map & join->eliminated_tables))
       {
         /* 
           When performing an outer join operation if there are no matching rows
@@ -3135,7 +3142,7 @@ make_join_statistics(JOIN *join, TABLE_LIST *tables_arg, COND *conds,
   }
 
   //psergey-todo: table elimination
-  eliminate_tables(join, &const_count, &found_const_table_map);
+  //eliminate_tables(join, &const_count, &found_const_table_map);
   //:psergey-todo
 
   /* Calc how many (possible) matched records in each table */
@@ -16517,7 +16524,7 @@ static void select_describe(JOIN *join, bool need_tmp_table, bool need_order,
 
       quick_type= -1;
 
-      //psergey-todo:
+      /* Don't show eliminated tables */
       if (table->map & join->eliminated_tables)
       {
         used_tables|=table->map;