postgresql - JDBC: Can I share a connection in a multithreading app, and enjoy nice transactions? -

-

it seems classical way handle transactions jdbc set auto-commit false. creates new transaction, , each call commit marks beginning next transactions. on multithreading app, understand common practice open new connection each thread.

i writing rmi based multi-client server application, server seamlessly spawning 1 thread each new connection. handle transactions correctly should go , create new connection each of thread ? isn't cost of such architecture prohibitive?

yes, in general need create new connection each thread. don't have control on how operating system timeslices execution of threads (notwithstanding defining own critical sections), inadvertently have multiple threads trying send data down 1 pipe.

note same applies network communications. if had 2 threads trying share 1 socket http connection, instance.

  • thread 1 makes request
  • thread 2 makes request
  • thread 1 reads bytes socket, unwittingly reading response thread 2's request

if wrapped transactions in critical sections, , therefore lock out other threads entire begin/commit cycle, might able share database connection between threads. wouldn't then, unless have innate knowledge of jdbc protocol.

if of threads have infrequent need database connections (or no need @ all), might able designate 1 thread database work, , have other threads queue requests 1 thread. reduce overhead of many connections. you'll have figure out how manage connections per thread in environment (or ask specific question on stackoverflow).

update: answer question in comment, database brands don't support multiple concurrent transactions on single connection (interbase/firebird exception know of).

it'd nice have separate transaction object, , able start , commit multiple transactions per connection. vendors don't support it.

likewise, standard vendor-independent apis jdbc , odbc make same assumption, transaction state merely property of connection object.


Comments

Post a Comment

Popular posts from this blog

c++ - How do I get a multi line tooltip in MFC -

-
right now, have tool tip pops when hover on edit box. problem tool tip contains multiple error messages , in 1 long line. need have each error message on own line. error messages contained in cstring new line seperating them. my existing code below. bool ontooltiptext(uint, nmhdr* pnmhdr, lresult* presult) { assert(pnmhdr->code == ttn_needtexta || pnmhdr->code == ttn_needtextw); // need handle both ansi , unicode versions of message tooltiptexta* pttta = (tooltiptexta*)pnmhdr; tooltiptextw* ptttw = (tooltiptextw*)pnmhdr; // tchar szfulltext[256]; cstring strtiptext=_t(""); uint nid = pnmhdr->idfrom; if (pnmhdr->code == ttn_needtexta && (pttta->uflags & ttf_idishwnd) || pnmhdr->code == ttn_needtextw && (ptttw->uflags & ttf_idishwnd)) { // idfrom hwnd of tool nid = ::getdlgctrlid((hwnd)nid); } //m_errprojaccel[ch] contains 1 or more error messages each...
Read more

asp.net - In javascript how to find the height and width -

-
i having .aspx , masterpage page. in masterpage loading aspx page . in aspx page design using generating table structure using code-behind server in javascript how find height , width . regards, kumar if you're looking table height , width, should it var tbl = document.getelementbyid('tbldemo'); alert(tbl.offsetwidth + '\n' + tbl.offsetheight);
Read more

c# - DataTable to EnumerableRowCollection -

-
i have datatable according client requirement can contain invalid date "00/00/1999",null,empty string.(typed datset) when collect them enumerables wish convert of invalid forms empty string. (i.e) enumerablerowcollection<datarow> query = order in _table.asenumerable() select new { orderdate= string.isnullorempty(convert.tostring(order.field<datetime>("orderdate")) || (how check date invalid date) ? string.empty : order.field<datetime>("orderdate") } how check whether date valid date or not? datetime.tryparse...like given current code: datetime date; enumerablerowcollection<datarow> query = order in _table.asenumerable() select new { orderdate= string.isnullorempty(convert.tostring(order.field<datetime>("orderdate")) || !datetime.tryparse(convert.tostring(order.field<datetime...
Read more