Re: A bug when use get_bit() function for a long bytea string

I want to resent the mail, because last one is in wrong format and hardly to read.

In addition, I think 'Size' or 'size_t' is rely on platform, they may can't work on 32bit

system. So I choose 'int64' after ashutosh's review.

>>I think the second argument indicates the bit position, which would be max bytea length * 8. If max bytea length covers whole int32, the second argument >needs to be wider i.e. int64.

>Yes, it makes sence and followed.

>>I think we need a similar change in byteaGetBit() and byteaSetBit() as well.

Sorry, I think it's my mistake, it is the two functions above should be changed.

>>Some more comments on the patch

>> struct pg_encoding

>> {

>>- unsigned (*encode_len) (const char *data, unsigned dlen);

>>+ int64 (*encode_len) (const char *data, unsigned dlen);

>>  unsigned (*decode_len) (const char *data, unsigned dlen);

>>  unsigned (*encode) (const char *data, unsigned dlen, char *res);

>>  unsigned (*decode) (const char *data, unsigned dlen, char *res);

>> Why not use return type of int64 for rest of the functions here as well?

>>  res = enc->encode(VARDATA_ANY(data), datalen, VARDATA(result));

>>  /* Make this FATAL 'cause we've trodden on memory ... */

>>- if (res > resultlen)

>>+ if ((int64)res > resultlen)

>>
>>if we change return type of all those functions to int64, we won't need this cast.

>I change the 'encode' function, it needs an int64 return type, but keep other 

>functions in 'pg_encoding', because I think it of no necessary reason.

>>Ok, let's leave it for a committer to decide. 

Well, I change all of them this time, because Tom Lane supports on next mail.

 

>Some more review comments.

>+   int64       res,resultlen;
>We need those on separate lines, possibly.

Done

>+   byteNo = (int32)(n / BITS_PER_BYTE);
>Does it hurt to have byteNo as int64 so as to avoid a cast. Otherwise, please
>add a comment explaining the reason for the cast. The comment applies at other
>places where this change appears.
>-       int         len;
>+       int64       len;
>Why do we need this change?
>        int         i;

It is my mistake as describe above, it should not be 'bitgetbit()/bitsetbit()'  to be changed.

>>It might help to add a test where we could pass the second argument something
>>greater than 1G. But it may be difficult to write such a test case.

>Add two test cases.

 
>+
>+select get_bit(
>+        set_bit((repeat('Postgres', 512 * 1024 * 1024 / 8))::bytea, 1024 * 1024 * 1024 + 1, 0)
>+       ,1024 * 1024 * 1024 + 1);

>This bit position is still within int4.
>postgres=# select pg_column_size(1024 * 1024 * 1024 + 1); 
> pg_column_size
>----------------
>              4   
>(1 row)

>You want something like
>postgres=# select pg_column_size(512::bigint * 1024 * 1024 * 8); 
> pg_column_size
>----------------
>              8   
>(1 row)

I intend to test size large then 1G, and now I think you give a better idea and followed.

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