Tom Lane wrote:
Andrew Chernow <[EMAIL PROTECTED]> writes:
There can be cases to use the same callbacks, although unlikely. To completely avoid collisions, the below would work:

Still looks like overdesign to me.  If we use the hook function address
we solve the problem with no extra notation and no extra storage.

Note that if you want N fixed keys, you can just have N hook functions
(all calling a shared workhorse routine, no doubt).  So your proposal
adds no functionality whatever if the usage involves a fixed number of
static handles.  Now it could possibly allow a variable-at-runtime
number of handles, but I'd want to see a worked-out use case before
designing for that much complexity.  In particular, it seems to me that
the problem would then shift to how do you know which handle to use for
the lookup, thus you've just introduced another layer of complexity
without buying anything.

I think the typical use case is just that you need to distinguish "your"
hook from anyone else's hooks, so the function address is plenty

It should also be noted that this whole problem *can* be solved without
any PQhookData at all: as long as you have hooks to get control at
creation and destruction of PGconns and PGresults, you can maintain your
own index data structure.  I'm willing to grant some amount of extra
API-stuff to save users having to do that in simple cases, but I don't
think we need to try to support infinitely complex cases.

                        regards, tom lane

Okay.  No problem over here.

Which callback do we use as the key? Currently, none are required (only the name was required). We have to choose one callback that must be provided. Maybe initHookData() must be provided? If the end-user doesn't need it they can just return NULL.

This is what is passed to PQaddObjectHooks, along with a conn:

typedef struct
  //char *name; REMOVED

  void *data;

  /* Invoked when PQsetObjectHook is called.  The pointer returned
   * by the hook implementation is stored in the private storage of
   * the PGconn, accessible via PQhookData(PGconn*).  If no
   * storage is needed, return NULL or set this hook to NULL.
  void *(*initHookData)(const PGconn *conn);

  /* Invoked on PQreset and PQresetPoll */
  void (*connReset)(const PGconn *conn);

  /* Invoked on PQfinish. */
  void (*connDestroy)(const PGconn *conn);

  /* Invoked on PQgetResult, internally called by all exec funcs */
  void *(*resultCreate)(const PGconn *conn, const PGresult *result);

  /* Invoked on PQcopyResult */
  void *(*resultCopy)(PGresult *dest, const PGresult *src);

  /* Invoked when PQclear is called */
  void (*resultDestroy)(const PGresult *result);
} PGobjectHooks;

Andrew Chernow
eSilo, LLC
every bit counts

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