Long Strings processing performance degradation in CH 18.12+

[den-crane]

Connected to ClickHouse server version 18.14.10 revision 54409.

"Macros" CREATE_INSERT:
create table xxxx (row String) engine=Memory;
insert into xxxx(row) select arrayStringConcat( arrayMap(x -> 'x'||toString(x)||':"'||toString(9999999)||'"',range(3000)), ',' )||',"test":"111",' from numbers(100000);

1. set max_block_size=65536;

2. CREATE_INSERT

3. select 1 from xxxx where row like '%test:0%'
   0 rows in set. Elapsed: 4.383 sec
   Processed 100.00 thousand rows, 4.69 GB (22.81 thousand rows/s., 1.07 GB/s.)

4. set max_block_size=5000;
   select 1 from xxxx where row like '%test:0%'
   0 rows in set. Elapsed: 4.546 sec

5. drop table xxxx;

6. exit / enter CH client
   set max_block_size=5000;
   CREATE_INSERT;

7. select 1 from xxxx where row like '%test:0%'
   0 rows in set. Elapsed: 0.963 sec.

8. set max_block_size=65536;
   select 1 from xxxx where row like '%test:0%';
   0 rows in set. Elapsed: 1.061 sec.

[den-crane]

The same server, downgrade to ClickHouse version 18.10.3.
select 1 from xxxx where row like '%test:0%'
0 rows in set. Elapsed: 0.686 sec. Processed 100.00 thousand rows, 4.69 GB (145.68 thousand rows/s., 6.83 GB/s.)

@KochetovNicolai is it somehow connected to LowCardinality ?

[den-crane]

fixed in 18.14.13 ?

Connected to ClickHouse server version 18.14.13 revision 54409.

SELECT 1 FROM xxxx WHERE row LIKE '%test:0%'

0 rows in set. Elapsed: 0.697 sec. Processed 100.00 thousand rows, 4.69 GB (143.42 thousand rows/s., 6.73 GB/s.)

[alexey-milovidov]

Yes. #3530