Re: [HACKERS] Function call hierarchy/path since getting the buffer until access its data
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
Re: [HACKERS] Function call hierarchy/path since getting the buffer until access its data
On Wed, May 30, 2012 at 9:37 AM, Waldecir Faria fighter2...@hotmail.com wrote: 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. heap_insert might be a good place to start. -- 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
Re: [HACKERS] Function call hierarchy/path since getting the buffer until access its data
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
