4 ms·

Thanks for the clarification. There is not automatically way to enlarge the length. And I think that is not the things should be done by the database itself. Th

Thanks for the clarification. There is not automatically way to enlarge the length. And I think that is not the things should be done by the database itself. That's my own opinion. But I think it would be helpful to show a warning to DBA when the allocated value is close to the upper limit. For the following question, the answer is in seconds. To enlarge the column length, TiDB just need to modify the meta data. "how long does it take to enlarge a pk column using alter table on a database that has a significant fraction of 4 billion rows?"

capableweb 6y ago
> we believe there is something we can do to help solve the database high availability and scalability problem > There is not automatically way to enlarge the length > I think that is not the things should be done by the database itself > would be helpful to show a warning to DBA So, in the end, TiDB does nothing to actually solve the problem they experienced but you still feel comfortable offering them your own solution? Sounds like you're a VP of Marketing, not a VP of Engineering. Leaves a very sour taste when spamming a forum like this. I hope your bosses don't read HN and sees your comments plugging TiDB everywhere where it's not relevant.
- neilhan 6y ago
  well said, we will take note; We were just trying to help anything related to MySQL's scalability
ithkuil 6y ago
> TiDB just need to modify the meta data. thanks, that's interesting. So existing data using the previous 32-bit encoded values happily coexist with the new data being written after the migration?
ithkuil 6y ago
> There is not automatically way to enlarge the length. And I think that is not the things should be done by the database itself. Sorry; it's hard to balance terseness with clarity. What I meant is to ask whether a tool such as Chaos-Mesh could have helped the github operations team to be aware of such a failure mode by causing this kinds of problems early. I think that's the purpose of chaos-engineering right? Some things happen too infrequently for us to plan for them, until when they finally do, causing problems that are more costly to solve than the cost of the prevention. It's still unclear to me whether this particular failure mode is common enough to be part of what a chaos-engineering tool explores by default; after all, not all databases around contain billions of rows. If engineers have to explicitly enable such a test because they are afraid of what would happen if a PK overflows, well, then probably they would take other preventive measures so that the problem doesn't happen in the first place (either preventively upgrading the size of the counter, or at least put some monitoring). I think what happened here is that a solution was designed when the database was way smaller; the user base grew and grew and this particular failure mode was overlooked (because there are many many other things to care about!). (I write this because I'm genuinely curious about what other people think about this topic, not to bash on parent for a shameless plug; I mentioned that only as a side comment; I heard good things about TiDB, I wish you well)
- user5994461 6y ago
  >>> It's still unclear to me whether this particular failure mode is common enough It is very common. Had the same thing happen in my company last year, on multiple systems! The organization was reaching a decade old, nobody thought of that when the table were initially created.
  - ithkuil 6y ago
    Yeah I now realize it's not necessarily 4billion rows actively used, but just 4billion unique keys being allocated

capableweb 6y ago

> we believe there is something we can do to help solve the database high availability and scalability problem > There is not automatically way to enlarge the length > I think that is not the things should be done by the database itself > would be helpful to show a warning to DBA So, in the end, TiDB does nothing to actually solve the problem they experienced but you still feel comfortable offering them your own solution? Sounds like you're a VP of Marketing, not a VP of Engineering. Leaves a very sour taste when spamming a forum like this. I hope your bosses don't read HN and sees your comments plugging TiDB everywhere where it's not relevant.

neilhan 6y ago
well said, we will take note; We were just trying to help anything related to MySQL's scalability

ithkuil 6y ago

> TiDB just need to modify the meta data. thanks, that's interesting. So existing data using the previous 32-bit encoded values happily coexist with the new data being written after the migration?

ithkuil 6y ago

> There is not automatically way to enlarge the length. And I think that is not the things should be done by the database itself. Sorry; it's hard to balance terseness with clarity. What I meant is to ask whether a tool such as Chaos-Mesh could have helped the github operations team to be aware of such a failure mode by causing this kinds of problems early. I think that's the purpose of chaos-engineering right? Some things happen too infrequently for us to plan for them, until when they finally do, causing problems that are more costly to solve than the cost of the prevention. It's still unclear to me whether this particular failure mode is common enough to be part of what a chaos-engineering tool explores by default; after all, not all databases around contain billions of rows. If engineers have to explicitly enable such a test because they are afraid of what would happen if a PK overflows, well, then probably they would take other preventive measures so that the problem doesn't happen in the first place (either preventively upgrading the size of the counter, or at least put some monitoring). I think what happened here is that a solution was designed when the database was way smaller; the user base grew and grew and this particular failure mode was overlooked (because there are many many other things to care about!). (I write this because I'm genuinely curious about what other people think about this topic, not to bash on parent for a shameless plug; I mentioned that only as a side comment; I heard good things about TiDB, I wish you well)

user5994461 6y ago
>>> It's still unclear to me whether this particular failure mode is common enough It is very common. Had the same thing happen in my company last year, on multiple systems! The organization was reaching a decade old, nobody thought of that when the table were initially created.
- ithkuil 6y ago
  Yeah I now realize it's not necessarily 4billion rows actively used, but just 4billion unique keys being allocated