Cockroach: sql: current sequence value not checked when updating min/max value

[mberhault]

Part of #21868
Minimalist reproduction:

on cockroach:

root@:26257/db> CREATE SEQUENCE t;
CREATE SEQUENCE

Time: 182.330804ms

root@:26257/db> SELECT nextval('t');
+---------+
| nextval |
+---------+
|       1 |
+---------+
(1 row)

Time: 42.495924ms

root@:26257/db> SELECT nextval('t');
+---------+
| nextval |
+---------+
|       2 |
+---------+
(1 row)

Time: 41.213481ms

root@:26257/db> ALTER SEQUENCE t MAXVALUE 1;
ALTER SEQUENCE

Time: 427.045439ms

root@:26257/db> SELECT nextval('t');
pq: nextval(): reached maximum value of sequence "t" (1)

The same occurs with a decrementing sequence and setting a minvalue.

On postgres, this fails on the ALTER SEQUENCE statement instead:

postgres=# CREATE SEQUENCE t;
CREATE SEQUENCE
postgres=# SELECT nextval('t');
 nextval 
---------
       1
(1 row)

postgres=# SELECT nextval('t');
 nextval 
---------
       2
(1 row)

postgres=# ALTER SEQUENCE t MAXVALUE 1;
ERROR:  MINVALUE (1) must be less than MAXVALUE (1)

[vilterp]

Thanks for finding this @mberhault. Fix coming soon.

[vivekmenezes]

if you're not working on a fix for this feel free to punt to 2.1

[vilterp]

Focused on clusterviz right now; punting.

[mberhault]

I'll chime in and say that this is not a critical issue and can definitely be pushed back.

[sploiselle]

@bobvawter Can I get a quick blurb describing this known limitation w/r/t the impact to user experience? Ideally, we need it by Friday 10/26 for the 2.1 Known Limitations page. Posting it on this issue and/or pinging me would be great.

[bobvawter]

@sploiselle,

Altering the minimum or maximum value of a series does not check the current value of a series. This means that it is possible to silently set the maximum to a value less than, or a minimum value greater than, the current value.