Question

I have a complicated SQL query executed from my application. The query runs fine with the version 3.6.11 (64ms). When run in 3.6.22 it takes more than 100 sec to finish. When executed from the command line client, the execution is quick both in 11 and 22. Therefore I want to run the query with "EXPLAIN" from inside my application. Is it possible? I tried to prepare and step the query and then read the column as as text but the result is empty.

Can be "EXPLAIN" executed from my application using C++ API ?

Answer 1

According to the SQLite opcode page :

Depending on compile-time options, you can put the SQLite virtual machine in a mode where it will trace its execution by writing messages to standard output. The non-standard SQL "PRAGMA" comments can be used to turn tracing on and off. To turn tracing on, enter:

PRAGMA vdbe_trace=on;

You can turn tracing back off by entering a similar statement but changing the value "on" to "off".

Also, the output from an EXPLAIN ... query is just a (an ordered) set of records that you can decode if you re up to it. See: this SQLite page

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