Re: Re: Call for platforms - Mailing list pgsql-hackers

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On 26 Mar 2001, at 23:14, Tom Lane wrote:

> "Mark Knox" <segfault@hardline.org> writes:
> > On 25 Mar 2001, at 16:07, Tom Lane wrote:
> >> Does that database have any user-created relations in it, or is it
> >> just a virgin database?
> 
> > Totally virgin. I created it just for that select you wanted.
> 
> Okay.   Would you create a couple of random tables in it and do the
> select again?  I want to see what ctid looks like in a user-created
> table.

Sure. I created two tables called 'test1' and 'test2'. Test1 has a 
single field 'field1' of type int4. Test2 has two fields 'field1' and 
'field2' of types char(200) and int4 respectively. 

Here are the results:

postgres=> select 
p1.oid,attrelid,relname,attname,attlen,attalign,attbyval from 
pg_attribute p1, pg_class p2 where atttypid = 27 and p2.oid = 
attrelid order by 1; oid|attrelid|relname       |attname|attlen|attalign|attbyval
- -----+--------+--------------+-------+------+--------+--------
16401|    1247|pg_type       |ctid   |     6|i       |f       
16415|    1262|pg_database   |ctid   |     6|i       |f       
16439|    1255|pg_proc       |ctid   |     6|i       |f       
16454|    1260|pg_shadow     |ctid   |     6|i       |f       
16464|    1261|pg_group      |ctid   |     6|i       |f       
16486|    1249|pg_attribute  |ctid   |     6|i       |f       
16515|    1259|pg_class      |ctid   |     6|i       |f       
16526|    1215|pg_attrdef    |ctid   |     6|i       |f       
16537|    1216|pg_relcheck   |ctid   |     6|i       |f       
16557|    1219|pg_trigger    |ctid   |     6|i       |f       
16572|   16567|pg_inherits   |ctid   |     8|i       |f       
16593|   16579|pg_index      |ctid   |     8|i       |f       
16610|   16600|pg_statistic  |ctid   |     8|i       |f       
16635|   16617|pg_operator   |ctid   |     8|i       |f       
16646|   16642|pg_opclass    |ctid   |     8|i       |f       
16678|   16653|pg_am         |ctid   |     8|i       |f       
16691|   16685|pg_amop       |ctid   |     8|i       |f       
16873|   16867|pg_amproc     |ctid   |     8|i       |f       
16941|   16934|pg_language   |ctid   |     8|i       |f       
16953|   16948|pg_largeobject|ctid   |     8|i       |f       
16970|   16960|pg_aggregate  |ctid   |     8|i       |f       
17038|   17033|pg_ipl        |ctid   |     8|i       |f       
17051|   17045|pg_inheritproc|ctid   |     8|i       |f       
17067|   17058|pg_rewrite    |ctid   |     8|i       |f       
17079|   17074|pg_listener   |ctid   |     8|i       |f       
17090|   17086|pg_description|ctid   |     8|i       |f       
17206|   17201|pg_toast_1215 |ctid   |     8|i       |f       
17221|   17216|pg_toast_17086|ctid   |     8|i       |f       
17236|   17231|pg_toast_1255 |ctid   |     8|i       |f       
17251|   17246|pg_toast_1216 |ctid   |     8|i       |f       
17266|   17261|pg_toast_17058|ctid   |     8|i       |f       
17281|   17276|pg_toast_16600|ctid   |     8|i       |f       
17301|   17291|pg_user       |ctid   |     8|i       |f       
17314|   17309|pg_rules      |ctid   |     8|i       |f       
17327|   17322|pg_views      |ctid   |     8|i       |f       
17342|   17335|pg_tables     |ctid   |     8|i       |f       
17355|   17350|pg_indexes    |ctid   |     8|i       |f       
18724|   18721|test1         |ctid   |     8|i       |f       
18735|   18731|test2         |ctid   |     8|i       |f       
(39 rows)

> > I suspect it might be an alignment problem
> 
> Sort of.  I am suspicious that sizeof(ItemPointerData) is returning 8
> rather than 6 as one might expect.

Maybe it's padding the structure to a dword boundary? ARM is 
notorious for such things.. I will rebuild it with 
__attribute__((packed)) on the struct and see if the size changes..


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