Thread: table-level and row-level locks.
<div style="background-color:"><div><div><div><div><div><div><div>Iam trying to acquire rowlevel locks in postgresql. I trydoing this: </div><div> 'select * from students where name='Larry' for update;</div><div>But by looking at the holdingarray of proclock , I've noticed that by doing this only <dl><dt>AccessShareLock gets acquired which is a table levellock. <dt>How do I acquire rowlevelock and what fields of Lock or Proclock datastructures indicate it.<dt>Thanks<dt>Jenny</dl></div></div></div></div></div></div></div></div><brclear="all" /><hr />MSN 8 helps <a href="http://g.msn.com/8HMVENUS/2752??PS=">ELIMINATEE-MAIL VIRUSES.</a> Get 2 months FREE*.
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>A row lock is represented by storing the locking transaction's ID in >xmax and setting the HEAP_MARKED_FOR_UPDATE infomask bit. Where is 'xmax' found? is it at code level or on disk? thanks Jenny >From: Tom Lane <tgl@sss.pgh.pa.us> >To: suzukikui@nttdata.co.jp >CC: pgsql-hackers@postgresql.org >Subject: Re: [HACKERS] table-level and row-level locks. Date: Wed, 20 Aug >2003 14:45:23 -0400 > >Koichi Suzuki <suzukikui@nttdata.co.jp> writes: > > I need to know where such "lock marks" are stored in the source level. > >A row lock is represented by storing the locking transaction's ID in >xmax and setting the HEAP_MARKED_FOR_UPDATE infomask bit. The bit is >needed to distinguish this from the case where the transaction is >deleting the tuple. > > regards, tom lane > >---------------------------(end of broadcast)--------------------------- >TIP 5: Have you checked our extensive FAQ? > > http://www.postgresql.org/docs/faqs/FAQ.html _________________________________________________________________ Get MSN 8 and help protect your children with advanced parental controls. http://join.msn.com/?page=features/parental
if table and page are locked in src/backend/storage/lmgr/lmgr.c by LockRelation() and LockPage respectively, in which file and by which function is a row locked? thanks Jenny >From: "Jenny -" <nat_lazy@hotmail.com> >To: pgsql-hackers@postgresql.org >Subject: Re: [HACKERS] table-level and row-level locks. >Date: Sun, 24 Aug 2003 11:30:41 -0700 > >>A row lock is represented by storing the locking transaction's ID in >>xmax and setting the HEAP_MARKED_FOR_UPDATE infomask bit. > >Where is 'xmax' found? is it at code level or on disk? >thanks >Jenny > > >>From: Tom Lane <tgl@sss.pgh.pa.us> >>To: suzukikui@nttdata.co.jp >>CC: pgsql-hackers@postgresql.org >>Subject: Re: [HACKERS] table-level and row-level locks. Date: Wed, 20 Aug >>2003 14:45:23 -0400 >> >>Koichi Suzuki <suzukikui@nttdata.co.jp> writes: >> > I need to know where such "lock marks" are stored in the source level. >> >>A row lock is represented by storing the locking transaction's ID in >>xmax and setting the HEAP_MARKED_FOR_UPDATE infomask bit. The bit is >>needed to distinguish this from the case where the transaction is >>deleting the tuple. >> >> regards, tom lane >> >>---------------------------(end of broadcast)--------------------------- >>TIP 5: Have you checked our extensive FAQ? >> >> http://www.postgresql.org/docs/faqs/FAQ.html > >_________________________________________________________________ >Get MSN 8 and help protect your children with advanced parental controls. >http://join.msn.com/?page=features/parental > > >---------------------------(end of broadcast)--------------------------- >TIP 8: explain analyze is your friend _________________________________________________________________ MSN 8: Get 6 months for $9.95/month. http://join.msn.com/?page=dept/dialup
>A row lock is represented by storing the locking transaction's ID in >xmax and setting the HEAP_MARKED_FOR_UPDATE infomask bit. The bit is >needed to distinguish this from the case where the transaction is >deleting the tuple. where is 'HEAP_MARKED_FOR_UPDATE infomask bit' found ? thanks >From: Tom Lane <tgl@sss.pgh.pa.us> >To: suzukikui@nttdata.co.jp >CC: pgsql-hackers@postgresql.org >Subject: Re: [HACKERS] table-level and row-level locks. Date: Wed, 20 Aug >2003 14:45:23 -0400 > >Koichi Suzuki <suzukikui@nttdata.co.jp> writes: > > I need to know where such "lock marks" are stored in the source level. > >A row lock is represented by storing the locking transaction's ID in >xmax and setting the HEAP_MARKED_FOR_UPDATE infomask bit. The bit is >needed to distinguish this from the case where the transaction is >deleting the tuple. > > regards, tom lane > >---------------------------(end of broadcast)--------------------------- >TIP 5: Have you checked our extensive FAQ? > > http://www.postgresql.org/docs/faqs/FAQ.html _________________________________________________________________ Use custom emotions -- try MSN Messenger 6.0! http://www.msnmessenger-download.com/tracking/reach_emoticon
On Sun, Sep 07, 2003 at 04:07:42PM -0700, Jenny - wrote: > >A row lock is represented by storing the locking transaction's ID in > >xmax and setting the HEAP_MARKED_FOR_UPDATE infomask bit. The bit is > >needed to distinguish this from the case where the transaction is > >deleting the tuple. > > where is 'HEAP_MARKED_FOR_UPDATE infomask bit' found ? Have you ever heard of the "grep" *nix utility? It's quite useful. Anyway, t_infomask is part of a struct called HeapTupleHeaderData, defined somewhere in src/include/access/htup.h -- Alvaro Herrera (<alvherre[a]dcc.uchile.cl>) You liked Linux a lot when he was just the gawky kid from down the block mowing your lawn or shoveling the snow. But now that he wants to date your daughter, you're not so sure he measures up. (Larry Greenemeier)