TidScan needs handling of a corner cases

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Hi All,

    I noticed that the TidScan fails to identify when the requested block
is
not in the relation. Consider this (pg_class has 6 blocks):

postgres=# explain analyze select ctid, * from pg_class where ctid in (
'(6,1)' );
ERROR:  could not read block 6 of relation 1663/11511/1259: read only 0 of
8192 bytes

    Also, it is known that 0 is not a valid row-offset in the block, but
the
tid input function accepts this value (it rejects -ve values). For the
same
setup:

postgres=#  explain analyze select ctid, * from pg_class where ctid in (
'(6,0)' );
                                             QUERY
PLAN
----------------------------------------------------------------------------------------------------
 Tid Scan on pg_class  (cost=0.00..4.01 rows=1 width=211) (actual
time=0.009..0.009 rows=0 loops=1)
   TID Cond: (ctid = '(6,0)'::tid)
 Total runtime: 0.130 ms
(3 rows)

    Can we safely fix these? First one by ignoring the request if
requested_block >= RelationGetNumberOfBlocks(), and second one by
accepting
only non-zero positive values in the tid input function.

Best regards

-- 
gurjeet[.singh]@[EMAIL PROTECTED]
 gmail | hotmail | indiatimes | yahoo }.com

EnterpriseDB http://www.enterprisedb.com

Mail sent from my BlackLaptop device

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Hi All,<br><br>&nbsp;&nbsp;&nbsp; I noticed that the TidScan fails to
identify when the requested block is not in the relation. Consider this
(pg_class has 6 blocks):<br><br>postgres=# explain analyze select ctid, *
from pg_class where ctid in ( &#39;(6,1)&#39; );<br>
ERROR:&nbsp; could not read block 6 of relation 1663/11511/1259: read only
0 of 8192 bytes<br><br>&nbsp;&nbsp;&nbsp; Also, it is known that 0 is not a
valid row-offset in the block, but the tid input function accepts this
value (it rejects -ve values). For the same setup:<br>
<br>postgres=#&nbsp; explain analyze select ctid, * from pg_class where
ctid in ( &#39;(6,0)&#39;
);<br>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
QUERY
PLAN&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<br>----------------------------------------------------------------------------------------------------<br>
&nbsp;Tid Scan on pg_class&nbsp; (cost=0.00..4.01 rows=1 width=211)
(actual time=0.009..0.009 rows=0 loops=1)<br>&nbsp;&nbsp; TID Cond: (ctid
= &#39;(6,0)&#39;::tid)<br>&nbsp;Total runtime: 0.130 ms<br>(3
rows)<br><br>&nbsp;&nbsp;&nbsp; Can we safely fix these? First one by
ignoring the request if&nbsp; requested_block &gt;=
RelationGetNumberOfBlocks(), and second one by accepting only non-zero
positive values in the tid input function.<br>
<br>Best regards<br><br>--
<br>gurjeet[.singh]@[EMAIL PROTECTED]
>singh.gurjeet@[EMAIL PROTECTED]
 gmail | hotmail |
indiatimes | yahoo }.com<br><br>EnterpriseDB <a
href="http://www.enterprisedb.com">http://www.enterprisedb.com</a><br><br>
Mail sent from my BlackLaptop device

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