On Tue, Dec 15, 2015 at 11:19 PM, Dominique Pell? <dominique.pelle at gmail.com > wrote:
> ??? <2004wqg2008 at 163.com> wrote: > > > > > After testing the Sqlite3_open and ATTACH DATABASE, > > I found that the attach database is slower than sqlite3_open. > > there is attachment after the mail which includ the speed > > information ( millisecond ). > > > Your attachment was discarded (attachment not allowed in this > mailing list). > > Anyway, I remember observing that: > > - sqlite3_open_v2(...) is lazy. In other words, it does not parse the > schema of the DB until the first query is performed after opening > the database. > - ATTACH is not lazy. The schema is parsed as soon as you > attach a database. > > That could explain the difference in speed. > Would there be a way to make ATTACH lazy by the way? > Why would that be of benefit to you? Are you intending to attach a database and never use it? It seems to me the same amount of time will be taken either way. When it comes to opening a database, there may be a need to do some connection specific configuration prior to actually opening the database file and parsing the schema. I believe this is the reason why open defers that processing until later, giving you a chance to finish configuring your connection before locking it down. Once that configuration is complete, there is no advantage to deferring the open of the database. I say no advantage ... maybe I just can't think of one. Why do you think there would be an advantage to deferring the open & schema processing of an attached database? -- Scott Robison
