On 2/21/2016 12:09 PM, Olivier Mascia wrote: > Is it possible to implement a SQL function > (https://www.sqlite.org/c3ref/create_function.html), which implementation > would be able to return the same value for the duration of the current > transaction? > > In other words, assume I'd like to implement some function which I could name > 'now()' which would return the current_timestamp as julian day, but would > return exactly the same value for any call made during the same transaction?
When I needed a stable version of now(), this is what I did. I had a global (well, actually, per-connection) time_t variable. I passed its address to sqlite3_create_function, to be retrieved within the custom function's implementation by means of sqlite3_user_data. The custom function would check this variable. If it's zero, it would obtain the current timestamp save it in that variable, and return it as its result; otherwise, it would return the previously-cached value. Whenever I started a new transaction, I reset the variable to zero. Luckily, I had a single spot issuing BEGIN statements (a C++ class wrapping SQLite connection handle; the time_t variable was also part of that class). -- Igor Tandetnik
