Thank you for the reply Robert. I think I am getting the idea about reading buffers but I am confused about the writing part, can you give me a function name where it does some write operations like creating a table or inserting a tuple for me read as a example.
Best Regards , -Waldecir > Date: Tue, 29 May 2012 11:33:59 -0400 > Subject: Re: [HACKERS] Function call hierarchy/path since getting the buffer > until access its data > From: robertmh...@gmail.com > To: fighter2...@hotmail.com > CC: pgsql-hackers@postgresql.org > > On Mon, May 28, 2012 at 8:15 AM, Waldecir Faria <fighter2...@hotmail.com> > wrote: > > Good morning, I am doing a study about buffer management to improve the > > performance of one program that does heavy I/O operations. After looking and > > reading from different softwares' source codes/texts one friend suggested me > > to take a look at the PostgreSQL code. I already took a look at the > > PostgreSQL buffer management modules ( freelist.c and cia ) but now I am a > > bit confused how the buffer read/write works, I tried to see how PostgreSQL > > does to get, for example, a char array from one buffer. Looking at rawpage.c > > I think that I found a good example using the following function calls > > sequence starting at function get_raw_page_internal(): > > > > StrategyGetBuffer->BufferAlloc->ReadBuffer_Common > > ->ReadBufferExtended->BufferGetPage-> memcpy page to buf > > BufferGetPage() doesn't copy anything; it just takes the buffer number > and returns a pointer to the address of that buffer in memory. More > generally, that whole chain of function calls has to do with how a > page ends up inside PostgreSQL's buffer cache, not with how anything > on the page is actually decoded. Each buffer contains zero or more > tuples; each tuple contains multiple attributes. So after you get the > buffer you have to iterate over the tuples and then decode each tuple > to get the values that you want. > > -- > Robert Haas > EnterpriseDB: http://www.enterprisedb.com > The Enterprise PostgreSQL Company > > -- > Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-hackers
