Pi Hydrae - Revision history

en>Kogge: wikilink Monthly Notices of the Royal Astronomical Society

2014-04-01T16:16:38Z

wikilink Monthly Notices of the Royal Astronomical Society

← Older revision		Revision as of 18:16, 1 April 2014
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	~~{{multiple issues\|~~		The title of the author is Jayson. Her family lives in Alaska but her spouse desires them to move. For years she's been operating as a travel agent. As a lady what she really likes is fashion and she's been performing it for fairly a while.<br><br>Feel free to visit my weblog; [http://srncomm.com/blog/2014/08/25/relieve-that-stress-find-a-new-hobby/ accurate psychic predictions]
	~~{{no footnotes\|date=October 2012}}~~
	~~{{refimprove\|date=November 2006}}~~
	}}
	~~A '''block-nested loop''' ('''BNL''') is an [[algorithm]] used to [[join (SQL)\|join]] two relations in a [[relational database]].~~

	~~This algorithm is a variation on~~ the simple [[nested loop join]] used to join two relations <math>R</math> and <math>S</math> (the "outer" and "inner" join operands, respectively). Suppose <math>\|R\| < \|S\|</math>. In a traditional nested loop join, <math>S</math> will be scanned once for every tuple of <math>R</math>. If there are many qualifying <math>R</math> tuples, and particularly if there is ~~no applicable index for the join key on <math>S</math>, this operation will be very expensive~~.

	The block nested loop join algorithm improves on the simple nested loop join by only scanning <math>S</math> once for every ''group'' of <math>R</math> tuples. For example, one variant of the block nested loop join reads an entire [[page (computing)\|page]] of <math>R</math> tuples into memory and loads them ~~into a [[hash table]]. It then scans <math>S</math>, and probes the hash table~~ to ~~find <math>S</math> tuples that match any of the tuples in the current page of <math>R</math>~~. ~~This reduces the number of scans of <math>S</math> that are necessary.~~

	~~A more aggressive variant of this algorithm loads as many pages of <math>R</math>~~ as ~~can be fit in the available memory, loading all such tuples into~~ a ~~hash table, and then repeatedly scans <math>S</math>. This further reduces the number of scans of <math>S</math> that are necessary~~. ~~In fact, this algorithm is essentially~~ a ~~special-case of the classic [[hash join]] algorithm.~~

	~~The block nested loop runs in <math>O(P_r P_s/M)</math> I/Os where <math>M</math>~~ is ~~the number of available pages of internal memory~~ and ~~<math>P_r</math> and <math>P_s</math> is size of <math>R</math> and <math>S</math> respectively in pages~~. ~~Note~~
	~~that block nested loop runs in <math>O(P_r+P_s)~~<~~/math~~> ~~I/Os if~~ <~~math~~>~~R</math> fits in the available internal memory.~~

	~~==References==~~
	~~{{Reflist}}~~
	* [http://~~dev.mysql~~.com/~~doc~~/~~refman~~/~~5.6~~/en/~~bnl~~-~~bka~~-~~optimization.html Block Nested~~-~~Loop Joins] in the MySQL 5.6 Reference Manual.~~

	~~{{DEFAULTSORT:Block Nested Loop}}~~
	~~[[Category:Join algorithms]~~]

en>Monkbot: /* References */Fix CS1 deprecated date parameter errors

2014-01-28T13:50:26Z

References: Fix CS1 deprecated date parameter errors

← Older revision		Revision as of 15:50, 28 January 2014
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	~~Claude~~ is ~~her name and she extended car~~ [~~http:~~//~~www~~.~~consumerautomotiveresearch.com~~/~~typesofwarranties~~.~~htm warranty completely] digs that title. Interviewing extended car [http:~~//~~www~~.~~nadelstich-mecky.de~~/index.~~php?mod=users&action=view&id=4380 auto warranty] is what she does but soon she~~'~~ll be on her own~~. ~~Delaware has usually been my~~ [~~http:~~/~~/racespace~~.~~org~~/~~groups~~/~~auto-repair-tips-make-your-car-running-smooth~~/ ~~extended auto warranty] living place and will never move~~. ~~One~~ of the ~~things I love most is [http:~~//~~Blog~~.~~Caranddriver.com/buying-peace~~-of~~-mind-how-to-buy-a-used-car-warranty/ climbing~~] ~~and now I have time to take on new things~~.<br><br>~~Visit my weblog :: [http:~~//~~Yardleyvashon.com~~/~~abig~~/~~ActivityFeed~~/~~MyProfile~~/~~tabid~~/~~381~~/~~UserId~~/~~1767/Default~~.~~aspx~~ http://~~Yardleyvashon~~.com/~~abig~~/~~ActivityFeed~~/~~MyProfile~~/~~tabid~~/~~381/UserId/1767/Default~~.~~aspx~~]		{{multiple issues\|
			{{no footnotes\|date=October 2012}}
			{{refimprove\|date=November 2006}}
			}}
			A '''block-nested loop''' ('''BNL''') is an [[algorithm]] used to [[join (SQL)\|join]] two relations in a [[relational database]].

			This algorithm is a variation on the simple [[nested loop join]] used to join two relations <math>R</math> and <math>S</math> (the "outer" and "inner" join operands, respectively). Suppose <math>\|R\| < \|S\|</math>. In a traditional nested loop join, <math>S</math> will be scanned once for every tuple of <math>R</math>. If there are many qualifying <math>R</math> tuples, and particularly if there is no applicable index for the join key on <math>S</math>, this operation will be very expensive.

			The block nested loop join algorithm improves on the simple nested loop join by only scanning <math>S</math> once for every ''group'' of <math>R</math> tuples. For example, one variant of the block nested loop join reads an entire [[page (computing)\|page]] of <math>R</math> tuples into memory and loads them into a [[hash table]]. It then scans <math>S</math>, and probes the hash table to find <math>S</math> tuples that match any of the tuples in the current page of <math>R</math>. This reduces the number of scans of <math>S</math> that are necessary.

			A more aggressive variant of this algorithm loads as many pages of <math>R</math> as can be fit in the available memory, loading all such tuples into a hash table, and then repeatedly scans <math>S</math>. This further reduces the number of scans of <math>S</math> that are necessary. In fact, this algorithm is essentially a special-case of the classic [[hash join]] algorithm.

			The block nested loop runs in <math>O(P_r P_s/M)</math> I/Os where <math>M</math> is the number of available pages of internal memory and <math>P_r</math> and <math>P_s</math> is size of <math>R</math> and <math>S</math> respectively in pages. Note
			that block nested loop runs in <math>O(P_r+P_s)</math> I/Os if <math>R</math> fits in the available internal memory.

			==References==
			{{Reflist}}
			* [http://dev.mysql.com/doc/refman/5.6/en/bnl-bka-optimization.html Block Nested-Loop Joins] in the MySQL 5.6 Reference Manual.

			{{DEFAULTSORT:Block Nested Loop}}
			[[Category:Join algorithms]]

en>Bibcode Bot: Adding 3 arxiv eprint(s), 0 bibcode(s) and 0 doi(s). Did it miss something? Report bugs, errors, and suggestions at User talk:Bibcode Bot

2012-09-01T01:34:50Z

Adding 3 arxiv eprint(s), 0 bibcode(s) and 0 doi(s). Did it miss something? Report bugs, errors, and suggestions at User talk:Bibcode Bot

New page

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