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write_transaction or stmt
one way get the cache length and then gtid length and then last event (mostly
query log event) and add them up and save into gtid packet
second way no calculation relie on actual binlog event writen in cache and then
write it into gtid event (fuck it wont work , what about fucking fsync and
i have to call write agian really bad idea)
so what the fuck to do
plan so far
we will be giing wia first method since secind meyhod will not work
there are three type if events one with comit one wi rollback and xid log event
so query log dvent and xid xheexkpoint eveent
it shhould be eastt yo get datta size from xid log but for qury we n3d to
do some shit.
one option mite bee to use fjxed length since there are onlyb2 options
for the time this is the the only solutiin --- asshole this wont work
So the plan right now
write_transaction_or_stmt
1. Rememember the current posiotion in cache (thread trx/stmt cache) (in case of
rollback and commit only , Xid event will have fixed lenght), why the not genneralize
it ?
2. write the event in cache(IO_CACHE) (how the fuck I will be doing i t, no clue)
3.read the whole cache length , trx and stmt
4 Pass it to write_gtid_event
::write()
No fucking clue
here babe
{
5984 Log_event_writer writer(&cache_data->cache_log, cache_data);
5985
5986 /*
5987 ┆ Write pending event to the cache.
5988 */
5989 DBUG_EXECUTE_IF("simulate_disk_full_at_flush_pending",
5990 ┆ ┆ ┆ ┆ {DBUG_SET("+d,simulate_file_write_error");});
5991 if (writer.write(pending))
5992 }
DDL
fuck me
So now for the writing in gtid_log_event
We will have the size of transaction - gtid_event_size
On the time of write , We need to have one flag
But how ? I mean we just have
bro i just explained that in #replication channel
see there
in shorrt extendable one byte flag every time when we over shoot
how to store thread id 4bytes
how we will be storing transaction size maybe use net_write_packet or 8 solid bytes
FOR THE TIME LETS HAVE 8 +4 no flexible , we will change it later
Circular buffer
Memeber variables
uchar* buffer;
uchar* buffer_end;
uint64 size;
uint elements;
/*
Some time we can have empty space in end if transaction/event is big to fit
in continues space.
*/
uchar* buffer_usable_ptr;
// Actual free space
uint64 usable_free_space;
uchar* write_head;
uchar* read_head;
uchar* flush_head;
std::mutex read_lock;
std::mutex write_lock;
Empty space for this case
S= Buffer_start
F= Flush Pointer
W= write pointer
E= buffer end
U= Buffer usable_ptr
if this case
S--F----W-----E
E - W + F -S
if this case
S--W-- F --- U--E
F-W
Write code
TS = Transaction size
if this case
S--F----W----E
if E-W > TS
then write data and W+= TS
if E-W < TS
buffer_usable_ptr= write_head
write_head= 0
It will become the second case
if this case
S--W----F--U--E
if TS < F -W
write
W+= TS
else
give error that buffer is full
and write into file
Read from queue
R < W
S--R---W--E
lock the mutex
R+= TS/ES
unlock the mutex
return the old read ptr
R > W
S--W---R--U--E
lock the mutex
R += TS/ES
if R == U
R= 0
unlock the mutex
return the old ptr
Bharthi no 02024407100 vandna mam
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