stasis-aries-wal/NOTES

create new record
	get a page with enough free space
		check existing pages for free space
		create a new emtpy page
	alloc a record on that page
		increment number of records on this page
		update free space pointer
write to record
	load the page into memory
		find the page on disk
		put the page in memory
		lock the page
	get the memory address of the record
		look up the record offset in the slot directory
	write to that record
	update log
	update lsn on page

read record
	load the page into memory
	get the address of the record
	read that record


begin xaction

commit xaction
	flush
	unlock

abort xaction
	delete page from memory	
	unlock

================================================================================

recordid memory.ralloc(int xid, size_t size) {
	for each page in the page table // page table are pages in RAM
		if locked, continue
			// context switch here SUCKS
		lock page
		break if freeSpace(page) >= size 
		free page
	if no free page
		create a new page and lock and load 

	

	return (recordid) page.recordAllocate(page, size)
	
}


void page.writeRecord(recordid rid, void *data) {
	
	assert page locked and loaded
	if xid and recordid is in hash table, do nothing
	else make shadow record	
	memcpy()

}


void *page.readRecord(recordid rid, void *buff) {
	make sure page is loaded
	memcpy()
	return pointer
}

commitXaction(int xid) {
	for each page that this xid has locked
		unlock page
		if pin count of page == 0
			flush


}


abortXaction(int xid) {
	for each locked page
		restore shadow records
		unlock page
		
}


================================================================================

transactional.c
	Tread
	Tbegin
	Tcommit
	Tabort
operations.h
	Tset
	Tdec
	Tinc
	
struct page {
	void *memAddr
	long lsn
	semaphore lock
}

bufferManager.c
	struct page loadPage(pageid)
	flushPage(struct page) // maybe take pageid
	dropPage(struct page) // maybe take pageid
	bufTransCommit(xid) // call flush and dropPage on page buffer
	bufTransAbort(xid) // call flush and dropPage on page buffer
	pin
	unpin

page.c
	rid ralloc(int size) // depends on bufferManager
	writeRecord(rid, data)
	readRecord(rid, buff)

recovery.c
logger.c
constants.h









==============================

buffer needs
 xid => ( pages )
 (dirty pages)
  page, first write LSN

page needs
 xid => ( recordids )
 xid,recordid => data


================
Testing

in main.c we can write something to the effect of

begin

write

for(;;)
	printf("looping");

commit

this way, when we see that "looping is printing, we can purposefully crash the program with control-c

not sure that this is anydifferent than having main.c {begin, write, exit}