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Re: Anyone here do anything with libpq?

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On 5/15/2017 11:38 AM, Rainer Weikusat wrote:
> DFS <nospam@dfs.com> writes:
>> https://www.postgresql.org/docs/9.6/static/libpq.html
>>
>> <quote>
>> PQclear
>> Frees the storage associated with a PGresult. Every command result
>> should be freed via PQclear when it is no longer needed.
>>
>> void PQclear(PGresult *res);
>>
>> You can keep a PGresult object around for as long as you need it; it
>> does not go away when you issue a new command, nor even if you close
>> the connection. To get rid of it, you must call PQclear. Failure to do
>> this will result in memory leaks in your application.
>> </quote>
>>
>> 'when it is no longer needed' sounds like it can be cleared once, at
>> the end of the script.
> 
> There seems to be some kind of fundamental misunderstanding about the
> nature of 'a result set' here. Specifically,
> 
> PGresult *res;
> 
> is a C pointer to a PGresult (structure) and in order to avoid memory
> leaks, the result this pointer points to has to be freed before the
> pointer is overwritten aka reused.
> 
> There's no need to free the result if the pointer won't be reused, IOW,
> if the application is going to end next, anyway.

The question is, if I use a PGresult 10x during a program, should I 
clear it between each use, or is one clear at the end OK?


In VB it's not necessary but I always closed them before the next usage.

Set rs = db.openrecordset("SELECT DATA;")
if rs.recordcount > 0 then
   ... do things
endif
rs.close

Set rs = db.openrecordset("SELECT DATA 2nd time;")
if rs.recordcount > 0 then
   ... do things
endif
rs.close

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Thread

Anyone here do anything with libpq? DFS <nospam@dfs.com> - 2017-05-15 10:41 -0400
  Re: Anyone here do anything with libpq? Rainer Weikusat <rweikusat@talktalk.net> - 2017-05-15 16:38 +0100
    Re: Anyone here do anything with libpq? DFS <nospam@dfs.com> - 2017-05-16 10:45 -0400
      Re: Anyone here do anything with libpq? Rainer Weikusat <rweikusat@talktalk.net> - 2017-05-16 20:52 +0100
  Re: Anyone here do anything with libpq? Robert Klemme <shortcutter@googlemail.com> - 2017-05-15 19:54 +0200
    Re: Anyone here do anything with libpq? DFS <nospam@dfs.com> - 2017-05-16 14:01 -0400
      Re: Anyone here do anything with libpq? Robert Klemme <shortcutter@googlemail.com> - 2017-05-16 23:04 +0200
      Re: Anyone here do anything with libpq? George Neuner <gneuner2@comcast.net> - 2017-05-17 08:40 -0400

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