On 9/16/17, David Wellman <dwell...@ward-analytics.com> wrote:
>
> Q1) I believe that the "sqlite3_prepare_v2" function parses the sql text to
> check it is valid, the named objects exist etc. and builds the 'executable
> program'. Does this function run the SQL? I don't think so.
>
sqlite3_prepare_v2() does not run your SQL. Usually. Actually, there
are a few PRAGMA statements that do get run immediately. For example
"PRAGMA foreign_keys=ON". But for all traditional SQL statements
("INSERT", "DELETE", "UPDATE", "SELECT", "CREATE", "DROP") the SQL is
not run until you call sqlite3_step()
>
> Q2) At what point in the interaction between an application and the SQLite
> engine is the sql actually executed? I think this is the first
> 'sqlite_step' function call.
It *starts* running on the first sqlite3_step() call. But it pauses
when the first row of output is generated. Execution continues on the
second sqlite3_step() call until another row is ready. And so forth.
>
> Q3) Are the 'sqlite_prepare' and 'sqlite_step' function calls synchronous?
> (By which I mean when called, will they wait to finish their processing
> before returning to the application).
Yes
>
> Just out of interest: Is the 'executable program' built by 'prepare' the
> 'virtual machine instructions' as referred to on the EXPLAIN documentation
> page (http://www.sqlite.org/lang_explain.html )?
>
Yes
--
D. Richard Hipp
d...@sqlite.org
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