On Wed, 2020-06-17 at 19:02 +0200, Matthias Apitz wrote: > We encountered that if our ESQL/C written servers see on SELECT or FETCH > in a row a NULL value, it will raise correctly the error -213 as written > and explained in https://www.postgresql.org/docs/11/ecpg-variables.html#ECPG-INDICATORS > We catch this error -213 and deal with in. > > What we did not knew and discovered today is something very fatal: In > such a situation on a FETCH of a row of some 55 columns, the transfer of > the column elements into their hostvariables stops on first NULL value, > as here to be seen in the log: > > [29217] [17.06.2020 15:49:16:499]: ecpg_execute on line 69: query: select * from acq_ffleit where bnr = $1 ; with 1 parameter(s) on connection sisis > [29217] [17.06.2020 15:49:16:500]: ecpg_execute on line 69: using PQexecParams > [29217] [17.06.2020 15:49:16:500]: ecpg_free_params on line 69: parameter 1 = 742 > [29217] [17.06.2020 15:49:16:500]: ecpg_process_output on line 69: correctly got 1 tuples with 55 fields > [29217] [17.06.2020 15:49:16:500]: ecpg_get_data on line 69: RESULT: 742 offset: 752; array: no > ... > [29217] [17.06.2020 15:49:16:500]: ecpg_get_data on line 69: RESULT: 49 offset: 752; array: no > [29217] [17.06.2020 15:49:16:500]: ecpg_get_data on line 69: RESULT: offset: 752; array: no > [29217] [17.06.2020 15:49:16:500]: raising sqlcode -213 on line 69: null value without indicator on line 69 > > In the above examples the transfer stopped after 47 RESULTs; the > hostvariables after this have been untouched in our program, i.e. only > part of the row has been read. > > One could say, "so what, you have error -213 and you deserve it". But at > least this behaviour should be documented clearly in the above mentioned page. > > I would expect, that NULL values would not be transfered in such case > but all other hostvariables yes, i.e. for me this is perhaps a bug in the > ESQL/C implementation. I think that is as expected. The documentation says: To be able to pass null values to the database or retrieve null values from the database, you need to append a second host variable specification to each host variable that contains data. This second host variable is called the *indicator* [...] Failure to do that causes an error (which you catch). If a statement causes an error, you cannot rely on the state of any host valiable that gets set by that statement. Yours, Laurenz Albe -- Cybertec | https://www.cybertec-postgresql.com
