[prev in list] [next in list] [prev in thread] [next in thread] 

List:       postgresql-general
Subject:    Re: [HACKERS] Add YAML option to explain
From:       daveg <daveg () sonic ! net>
Date:       2009-08-31 20:06:29
Message-ID: 20090831200629.GR9321 () sonic ! net
[Download RAW message or body]

On Mon, Aug 31, 2009 at 02:15:08PM -0000, Greg Sabino Mullane wrote:
> > Greg, can we see a few examples of the YAML output
> > compared to both json and text?
...
> greg=# explain (format json, analyze on) select * from pg_class where relname ~ 'x' order by 1,2,3;
>                         QUERY PLAN
> - -----------------------------------------------------------

An interesting property of json, it is almost exactly the same as python
data structure syntax. If I paste the following into python:

plan = [
         {
           "Plan": {
             "Node Type": "Sort",
             "Startup Cost": 12.82,
             "Total Cost": 13.10,
             "Plan Rows": 111,
             "Plan Width": 185,
             "Actual Startup Time": 1.152,
             "Actual Total Time": 1.373,
             "Actual Rows": 105,
             "Actual Loops": 1,
             "Sort Key": ["relname", "relnamespace", "reltype"],
             "Sort Method": "quicksort",
             "Sort Space Used": 44,
             "Sort Space Type": "Memory",
             "Plans": [
               {
                 "Node Type": "Seq Scan",
                 "Parent Relationship": "Outer",
                 "Relation Name": "pg_class",
                 "Alias": "pg_class",
                 "Startup Cost": 0.00,
                 "Total Cost": 9.05,
                 "Plan Rows": 111,
                 "Plan Width": 185,
                 "Actual Startup Time": 0.067,
                 "Actual Total Time": 0.817,
                 "Actual Rows": 105,
                 "Actual Loops": 1,
                 "Filter": "(relname ~ 'x'::text)"
               }
             ]
           },
           "Triggers": [
           ],
           "Total Runtime": 1.649
         }
       ]

I get a python data structure. Which can be manipulated directly, or pretty
printed:

>>> import pprint
>>> pprint.pprint(plan)
[{'Plan': {'Actual Loops': 1,
           'Actual Rows': 105,
           'Actual Startup Time': 1.1519999999999999,
           'Actual Total Time': 1.373,
           'Node Type': 'Sort',
           'Plan Rows': 111,
           'Plan Width': 185,
           'Plans': [{'Actual Loops': 1,
                      'Actual Rows': 105,
                      'Actual Startup Time': 0.067000000000000004,
                      'Actual Total Time': 0.81699999999999995,
                      'Alias': 'pg_class',
                      'Filter': "(relname ~ 'x'::text)",
                      'Node Type': 'Seq Scan',
                      'Parent Relationship': 'Outer',
                      'Plan Rows': 111,
                      'Plan Width': 185,
                      'Relation Name': 'pg_class',
                      'Startup Cost': 0.0,
                      'Total Cost': 9.0500000000000007}],
           'Sort Key': ['relname', 'relnamespace', 'reltype'],
           'Sort Method': 'quicksort',
           'Sort Space Type': 'Memory',
           'Sort Space Used': 44,
           'Startup Cost': 12.82,
           'Total Cost': 13.1},
  'Total Runtime': 1.649,
  'Triggers': []}]

I'm not sure if all json can be read this way, but the python and json
notations are very similar.

-dg

--
David Gould       daveg@sonic.net      510 536 1443    510 282 0869
If simplicity worked, the world would be overrun with insects.

-- 
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers
[prev in list] [next in list] [prev in thread] [next in thread]