Skip calling rocksdb::GetApproximateSize is start >= limit (#131)

Summary:
When kd::successor() is called in records_in_range, there is a
possiblity of range.start >= range.limit. RocksDB has an assertion
"v->cfd_->internal_comparator().Compare(start, end) <= 0'" so
range should not be passed to rocksdb::GetApproximateSize in that case.
This diff skips calling rocksdb::GetApproximateSize() and just returns
0.

Test Plan: mtr and rocksdb.rocksdb

Reviewers: jkedgar, spetrunia, hermanlee4

Reviewed By: hermanlee4

Subscribers: webscalesql-eng

Differential Revision: https://reviews.facebook.net/D52491

mysql-test/suite/rocksdb/r/rocksdb.result

@@ -2172,4 +2172,15 @@ insert into t2
 select concat('v-', 100 + A.a*100 + B.a), 12345 from t1 A, t1 B;
 update t2 set a=concat('x-', a) where a between 'v-1002' and 'v-1004';
 drop table t1,t2;
+#
+# Issue #131: Assertion `v->cfd_->internal_comparator().Compare(start, end) <= 0' failed
+#
+CREATE TABLE t2(c1 INTEGER UNSIGNED NOT NULL, c2 INTEGER NULL, c3 TINYINT, c4 SMALLINT , c5 MEDIUMINT, c6 INT, c7 BIGINT, PRIMARY KEY(c1,c6)) ENGINE=RocksDB;
+INSERT INTO t2 VALUES (1,1,1,1,1,1,1);
+SELECT * FROM t2 WHERE c1 > 4294967295 ORDER BY c1,c6;
+c1	c2	c3	c4	c5	c6	c7
+EXPLAIN SELECT * FROM t2 WHERE c1 > 4294967295 ORDER BY c1,c6;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	NULL	NULL	NULL	NULL	NULL	NULL	NULL	Impossible WHERE noticed after reading const tables
+drop table t2;
 SET GLOBAL ROCKSDB_PAUSE_BACKGROUND_WORK = @ORIG_PAUSE_BACKGROUND_WORK;

mysql-test/suite/rocksdb/t/rocksdb.test

@@ -1744,4 +1744,13 @@ update t2 set a=concat('x-', a) where a between 'v-1002' and 'v-1004';
 
 drop table t1,t2;
 
+--echo #
+--echo # Issue #131: Assertion `v->cfd_->internal_comparator().Compare(start, end) <= 0' failed
+--echo #
+CREATE TABLE t2(c1 INTEGER UNSIGNED NOT NULL, c2 INTEGER NULL, c3 TINYINT, c4 SMALLINT , c5 MEDIUMINT, c6 INT, c7 BIGINT, PRIMARY KEY(c1,c6)) ENGINE=RocksDB;
+INSERT INTO t2 VALUES (1,1,1,1,1,1,1);
+SELECT * FROM t2 WHERE c1 > 4294967295 ORDER BY c1,c6;
+EXPLAIN SELECT * FROM t2 WHERE c1 > 4294967295 ORDER BY c1,c6;
+drop table t2;
+
 SET GLOBAL ROCKSDB_PAUSE_BACKGROUND_WORK = @ORIG_PAUSE_BACKGROUND_WORK;

storage/rocksdb/ha_rocksdb.cc

@@ -6444,6 +6444,12 @@ ha_rows ha_rocksdb::records_in_range(uint inx, key_range *min_key,
   rocksdb::Slice slice1((const char*) sec_key_packed_tuple, size1);
   rocksdb::Slice slice2((const char*) sec_key_packed_tuple_old, size2);
 
+  // slice1 >= slice2 means no row will match
+  if (slice1.compare(slice2) >= 0)
+  {
+    DBUG_RETURN(0);
+  }
+
   rocksdb::Range r(
     kd->is_reverse_cf ? slice2 : slice1,
     kd->is_reverse_cf ? slice1 : slice2