Message-ID: <4FEB10D6.4050204@enterprisedb.com>
Date: Wed, 27 Jun 2012 16:55:34 +0300
From: Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>
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To: Andres Freund <andres@2ndquadrant.com>
CC: pgsql-hackers@postgresql.org
Subject: Re: [PATCH 07/16] Log enough data into the wal to reconstruct logical
	changes from it if wal_level=logical
References: <201206131327.24092.andres@2ndquadrant.com>
	<1339586927-13156-7-git-send-email-andres@2ndquadrant.com>
In-Reply-To: <1339586927-13156-7-git-send-email-andres@2ndquadrant.com>
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On 13.06.2012 14:28, Andres Freund wrote:
> @@ -2584,6 +2610,73 @@ l1:
>   		rdata[1].buffer_std = true;
>   		rdata[1].next = NULL;
>
> +		/*
> +		 * XXX: We could decide not to log changes when the origin is not the
> +		 * local node, that should reduce redundant logging.
> +		 */
> +		if(need_tuple){
> +			xl_heap_header xlhdr;
 > ...
> +			relationFindPrimaryKey(relation,&indexoid,&pknratts, pkattnum, pktypoid, pkopclass);
> +
> +			if(!indexoid){
> +				elog(WARNING, "Could not find primary key for table with oid %u",
> +				     relation->rd_id);
> +				goto no_index_found;
> +			}
> +
> +			index_rel = index_open(indexoid, AccessShareLock);
> +
> +			indexdesc = RelationGetDescr(index_rel);
> +
> +			for(natt = 0; natt<  indexdesc->natts; natt++){
> +				idxvals[natt] =
> +					fastgetattr(&tp, pkattnum[natt], desc,&idxisnull[natt]);
> +				Assert(!idxisnull[natt]);
> +			}
> +
> +			idxtuple = heap_form_tuple(indexdesc, idxvals, idxisnull);
> +
> +			xlhdr.t_infomask2 = idxtuple->t_data->t_infomask2;
> +			xlhdr.t_infomask = idxtuple->t_data->t_infomask;
> +			xlhdr.t_hoff = idxtuple->t_data->t_hoff;
> +
> +			rdata[1].next =&(rdata[2]);
> +			rdata[2].data = (char*)&xlhdr;
> +			rdata[2].len = SizeOfHeapHeader;
> +			rdata[2].buffer = InvalidBuffer;
> +			rdata[2].next = NULL;
> +
> +			rdata[2].next =&(rdata[3]);
> +			rdata[3].data = (char *) idxtuple->t_data + offsetof(HeapTupleHeaderData, t_bits);
> +			rdata[3].len = idxtuple->t_len - offsetof(HeapTupleHeaderData, t_bits);
> +			rdata[3].buffer = InvalidBuffer;
> +			rdata[3].next = NULL;
> +
> +			heap_close(index_rel, NoLock);
> +		no_index_found:
> +			;
> +		}
> +
>   		recptr = XLogInsert(RM_HEAP_ID, XLOG_HEAP_DELETE, rdata);
>
>   		PageSetLSN(page, recptr);

It's not cool to do all that primary key lookup stuff within the 
critical section, while holding a lock on the page.

-- 
   Heikki Linnakangas
   EnterpriseDB   http://www.enterprisedb.com