Re: machine-readable explain output v4 - Mailing list pgsql-hackers

Hi Robert, Hi all,

On Thursday 30 July 2009 05:05:48 Robert Haas wrote:
> OK, here's the updated version of my machine-readable explain output
> patch.  This needed heavy updating as a result of the changes that Tom
> asked me to make to the explain options patch, and the further changes
> he made himself.  In addition to any regressions I may have introduced
> during the rebasing process, there is one definite problem here: in
> the previous version of this patch, explain (format xml) returned XML
> data; now, it's back to text.

> The reason for this regression is that Tom asked me to change
> ExplainStmt to just carry a list of nodes and to do all the parsing in
> ExplainQuery.  Unfortunately, the TupleDesc is constructed by
> ExplainResultDesc() which can't trivially be changed to take an
> ExplainState, because UtilityTupleDescriptor() also wants to call it.
> We could possibly fix this by a hack similar to the one we already
> added to GetCommandLogLevel(), but I haven't done that here.
Hm. I think its cleaner to move the option parsing into its own function - its
3 places parsing options then and probably not going to get less.
I am not sure this is cleaner than including the parsed options in ExplainStm
though... (possibly in a separate struct to avoid changing copy/equal-funcs
everytime)

Some more comments on the (new) version of the patch:
- The regression tests are gone?
- Currently a value scan looks like »Values Scan on "*VALUES*"« What about
adding its alias at least in verbose mode? This currently is inconsistent with
other scans. Also he output columns of a VALUES scan are named column$N even
if names as specified like in AS foo(colname)
- why do xml/json contain no time units anymore? (e.g. Total Runtime).
Admittedly thats already inconsistent in the current text format...

- Code patterns like:    if (es->format == EXPLAIN_FORMAT_TEXT)        appendStringInfo(es->str, "Total runtime: %.3f
ms\n",                        1000.0 * totaltime);    else if (es->format == EXPLAIN_FORMAT_XML)
appendStringInfo(es->str,                        "    <Total-Runtime>%.3f</Total-Runtime>\n",
1000.0* totaltime);    else if (es->format == EXPLAIN_FORMAT_JSON)        appendStringInfo(es->str, ",\n    \"Total
runtime\": %.3f",                         1000.0 * totaltime); 
or         if (es->format == EXPLAIN_FORMAT_TEXT)            appendStringInfo(es->str, " for constraint %s", conname);
     else if (es->format == EXPLAIN_FORMAT_XML)        {            appendStringInfoString(es->str, "
<Constraint-Name>");           escape_xml(es->str, conname);            appendStringInfoString(es->str,
"</Constraint-Name>\n");       }        else if (es->format == EXPLAIN_FORMAT_JSON)        {
appendStringInfo(es->str,"\n        \"Constraint Name\": ");            escape_json(es->str, conname);        } 

possibly could be simplified using ExplainPropertyText or a function accepting
a format string.
At least for the !EXPLAIN_FORMAT_TEXT this seems simple at multiple places in
ExplainOnePlan and report_triggers.


On Friday 31 July 2009 23:13:54 Robert Haas wrote:
> On Sat, Jul 18, 2009 at 10:29 PM, Andres Freund<andres@anarazel.de> wrote:
> > One part where I find the code flow ugly is 'did_boilerplate' in
> > report_triggers/its callsites.
> > I can see why it is done that way, but its not exactly obvious to read
> > when you want to find out how the format looks.
> Suggestions?
The only idea without building more xml/json infrastructure I have is using a
separate stringbuffer inside report_triggers - but thats not much nicer.

Thats all I could find right now...

Andres