Re: [GSoC2014] Patch ALTER TABLE ... SET LOGGED - Mailing list pgsql-hackers

<div dir="ltr"><div class="gmail_extra"><br /><br />On Thu, Jul 17, 2014 at 8:02 PM, Andres Freund <<a
href="mailto:andres@2ndquadrant.com"target="_blank">andres@2ndquadrant.com</a>> wrote:<br />><br />> > That
meansshould I "FlushRelationBuffers(rel)" before change the<br /> > > relpersistence?<br />><br />> I don't
thinkthat'd help. I think what this means that you simply<br />> cannot change the relpersistence of the old
relationbefore the heap<br />> swap is successful. So I guess it has to be something like (pseudocode):<br />
><br/>> OIDNewHeap = make_new_heap(..);<br />> newrel = heap_open(OIDNewHeap, AEL);<br />><br />> /*<br
/>> * Change the temporary relation to be unlogged/logged. We have to do<br />>  * that here so buffers for the
newrelfilenode will have the right<br /> >  * persistency set while the original filenode's buffers won't get
read<br/>>  * in with the wrong (i.e. new) persistency setting. Otherwise a<br />>  * rollback after the rewrite
wouldpossibly result with buffers for the<br /> >  * original filenode having the wrong persistency setting.<br
/>> *<br />>  * NB: This relies on swap_relation_files() also swapping the<br />>  * persistency. That
wouldn'twork for pg_class, but that can't be<br /> >  * unlogged anyway.<br />>  */<br />>
AlterTableChangeCatalogToLoggedOrUnlogged(newrel);<br/>> FlushRelationBuffers(newrel);<br />> /* copy heap data
intonewrel */<br />> finish_heap_swap();<br />><br />> And then in swap_relation_files() also copy the
persistency.<br/> ><br />><br />> That's the best I can come up right now at least.<br />><br /><br
/></div><divclass="gmail_extra">Isn't better if we can set the relpersistence as an argument to "make_new_heap" ?<br
/><br/></div><div class="gmail_extra">I'm thinking to change the make_new_heap:<br /></div><div class="gmail_extra"><br
/></div><divclass="gmail_extra">From: <br /></div><div class="gmail_extra"><br /> make_new_heap(Oid OIDOldHeap, Oid
NewTableSpace,bool forcetemp,<br />                LOCKMODE lockmode)<br /><br /></div><div class="gmail_extra">To:<br
/><br/> make_new_heap(Oid OIDOldHeap, Oid NewTableSpace, char relpersistence,<br />               LOCKMODE lockmode)<br
/><br/></div><div class="gmail_extra"> That way we can create the new heap with the appropriate relpersistence, so in
theswap_relation_files also copy the persistency, of course.<br /></div><div class="gmail_extra"><br /></div><div
class="gmail_extra">Andafter copy the heap data to the new table (ATRewriteTable) change relpersistence of the
OldHeap'sindexes, because in the "finish_heap_swap" they'll be rebuild.<br /></div><div class="gmail_extra"><br
/></div><divclass="gmail_extra">Thoughts?<br /></div><div class="gmail_extra"><br /></div><div
class="gmail_extra">Regards,<br/><br /></div><div class="gmail_extra">--<br />Fabrízio de Royes Mello<br />
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