fix(test): datagen parallel e2e (#3840)

Signed-off-by: Bugen Zhao <i@bugenzhao.com>

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

e2e_test/streaming/datagen.slt

@@ -7,8 +7,9 @@ create materialized source s1 (v1 int, v2 float) with ( 'connector' = 'datagen'
 # Wait enough time to ensure Datagen connector generate data
 sleep 2s
 
+# Will only generate 10 records since `fields.v1.end` is 10
 query II rowsort
-select v1, v2 from s1 limit 15;
+select v1, v2 from s1 where v1 is not null limit 15;
 ----
 1 11
 2 12
@@ -20,11 +21,6 @@ select v1, v2 from s1 limit 15;
 8 18
 9 19
 10 20
-NULL NULL 
-NULL NULL 
-NULL NULL 
-NULL NULL 
-NULL NULL 
 
 statement ok
 drop source s1;
@@ -37,18 +33,18 @@ create materialized source s1 (v1 int)  with ( 'connector' = 'datagen' ,'fields.
 sleep 2s
 
 query II rowsort
-select v1 from s1 order by v1 limit 10;
+select v1 from s1 where v1 is not null limit 10;
 ----
 1
-2 
-3 
-4 
-5 
-6 
+2
+3
+4
+5
+6
 7
-8 
+8
 9
 10
 
 statement ok
-drop source s1;
+drop source s1;