Hi, > Does this mean that H2 now creates primary indexes on non integer based columns?
> This indicated that a hidden BigInt column would be created and that would become the primary index. Yes, if the primary key is not a bigint, a hidden column is created (the _rowid_ column), and the data is stored with this as the key. The question is whether you want to call this column the "primary key" as it's not the (user visible) primary key. I wrote: "You have two indexes (one primary key, and a secondary key)", in this case I meant the user visible primary key. Regards, Thomas On Wed, Feb 5, 2014 at 9:37 PM, Roger Thomas <[email protected]>wrote: > >> Well, this is actually relevant. You have two indexes (one primary key, >> and a secondary key) on randomly distributed data. There is no way to make >> it really fast, unless it fits in memory. Having to use an index on >> randomly distributed data is a "cache killer". All you can really do in >> this case is try to load everything in memory, or use a solid state disk. >> >> Because of that, I would avoid an index on randomly distributed data (no >> matter what database is storage system you use), unless you know in advance >> that the number of entries will never grow beyond a certain size, or unless >> the amount of data you store is so big that the lookup cost (at most 200 >> per second for a regular hard disk) is lower than the amount of data. That >> means, each entry is about 2 MB in size or larger. >> > > >> Regards, >> Thomas >> >> >> Does this mean that H2 now creates primary indexes on non integer based > columns? The only info I could find was from a post of yours on > stackoverflow from Oct 2010. This indicated that a hidden BigInt column > would be created and that would become the primary index. > > -- > You received this message because you are subscribed to the Google Groups > "H2 Database" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > Visit this group at http://groups.google.com/group/h2-database. > For more options, visit https://groups.google.com/groups/opt_out. > -- You received this message because you are subscribed to the Google Groups "H2 Database" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/h2-database. For more options, visit https://groups.google.com/groups/opt_out.
