Re: pgbench stats per script & other stuff

On Fri, Feb 5, 2016 at 12:53 AM, Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr> wrote:
>> Something is wrong with patch d. I noticed two things,
>> 1. the total_weight stuff can overflow,
>
> It can generate an error on overflow by checking the total_weight while it
> is being computed. I've switched total_weight to int64 so it is now really
> impossible to overflow with the 32 bit int_max limit on weight.

+ /* compute total_weight */
+ for (i = 0; i < num_scripts; i++)
+ {
+ total_weight += sql_script[i].weight;
+
+ /* detect overflow... */
+ if (total_weight < 0)
+ {
+ fprintf(stderr, "script weight overflow at
script %d\n", i+1);
+ exit(1);
+ }
+ }
If let as int64, you may want to remove this overflow check, or keep
it as int32.

>> 2. the chooseScript stuff is broken, or something.
>
> Sorry, probably a <=/< error. I think I've fixed it and I've simplified the
> code a little bit.

+ w = getrand(thread, 0, total_weight - 1);
+ do
+ {
+ w -= sql_script[i++].weight;
+ } while (w >= 0);
+
+ return i - 1;
This portion looks fine to me.

>> Another thing is that the "transaction type" output really deserves some
>> more work. I think "multiple scripts" really doesn't cut it; we should
>> have some YAML-like as in the latency reports, which lists all scripts
>> in use and their weights.
>
> For me the current output is clear for the reader, which does not mean that
> it cannot be improve, but how is rather a matter of taste.
>
> I've tried to improve it further, see attached patch.
>
> If you want something else, it would help to provide a sample of what you
> expect.

You could do that with an additional option here as well:
--output-format=normal|yamljson. The tastes of each user is different.
>> Attached is my version of the patch. While you're messing with it, it'd
>> be nice if you added comments on top of your recently added functions
>> such as findBuiltin, process_builtin, chooseScript.
> Why not.

const char *name;
+ int weight;
Command **commands;
- StatsData stats;
+ StatsData stats;
Noise here?

> Find attached a 18-d which addresses these concerns, and a actualized 18-e
> for the prefix.

(I could live without that personally)

-/* return builtin script "name", or fail if not found */
+/* return commands for selected builtin script, if unambiguous */
static script_t *
findBuiltin(const char *name)
This comment needs a refresh. This does not return a set of commands,
but the script itself.
--
Michael