Hello,
> We almost never pass a ready-made query, but use dynamic queries most of the
> time.
>
> When we do:
> cppdb::result res = sql << "SELECT * FROM user WHERE id = ? << user_id;
> it's very useful in many circumstances to know which user_id was actually
> passed.
> Internally, cppdb must be creating the full query before passing it to the
> backend.
> I need to have the full query with the replacements made:
> "SELECT * FROM user WHERE id = 123"
That is exactly what you are not going to get as CppDB uses almost anywhere
prepared statements, that means that query that is passed is actually:
"SELECT * FROM user WHERE id = ?"
And parameter was binded separately on the Specific DB API level, like
PQexecParams
or PQexecPrepared
This gives significant performance boost (100%-200%) as statements are prepared
only
once and the parameters are transferred independently.
So don't expect to make this helpful.
Also you should remember that the query itself is not globally available so for
example
if result binding fails there is no way to get the query itself or in many cases
the prepared statement already lost the information about the original query
as it keeps its statement object rather then the query itself.
>
> Moreover, in a real application, some queries can become increasingly complex
> and increasingly dynamic (e.g. see Drupal and some of its API like
> db_rewrite_query()...!)
> Often, in order to understand why we don't get the result we expect, we need
> to have the very exact query as run by the SQL server.
Generally it is good idea not to generate SQL queries on the fly but rather
create a set of statements you use and pass parameters via prepared statements.
>
> I don't understand the cppdb internals and don't understand your first point
> ("the query just does not exists or is invalid").
> But surely, at some point you must be sending a full query to the server, so
> it should be fairly easy to retrieve it.
This is exactly the point, it is not. It may become some server side object
and the call actually would look like:
exec prepared cppdb_stmt_3(123);
This library has very different internals in comparison to dbixx.
Artyom
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