On Thu, Oct 24, 2013 at 8:19 PM, Pavel Cisar <pcisar@...> wrote:

 

Hi,

Dne 24.10.2013 17:21, Harriv napsal(a):

>
> 2. Data arrives immediately - after I have stopped tracing with tracex.
>
> If I run this configuration with fbtracemgr:
>
> <database MYDATABASENAME>
> enabled true
> log_statement_finish true
> print_plan true
> include_filter %%SELECT%%
> exclude_filter %%RDB$%%
> time_threshold 0
> max_sql_length 2048
> </database>
>
> Output is printed immediately.

Well, I see where the problem is now. There are two methods how to
retrieve output from services via isc_service_query API call:

a) using isc_info_svc_line request that reads single line per call.
b) using isc_info_svc_to_eof request that fills the buffer provided by
client. It doesn't return until buffer is full or EOF is reached.

Because services typically provide output with a lot of lines, FDB uses
the second method as it transfers data from server to client
significantly faster. Service.readline() method works on top of this
buffer, so you'll get it's content as individual lines. However, FDB
uses 64K buffer, so you'll not get any output until engine provides 64K
of text for you.

If you want to get service output by first query method, you have to
query for it yourself. There is fdb.Service._QS() helper method for that.

Example loop that fetches service output by line:

while 1:
try:
line = svc._QS(fdb.ibase.isc_info_svc_line)
except fdb.OperationalError:
# It is routine for actions such as RESTORE to raise an
# exception at the end of their output. We ignore any such
# exception and assume that it was expected, which is somewhat
# risky. For example, suppose the network connection is broken
# while the client is receiving the action's output...
break
if not line: # we reached the end of output
break
print line

best regards
Pavel Cisar
IBPhoenix