Innodb 索引结构了解 - Innodb Index Structure(转)

Innodb 作为 MySQL 中使用最为广泛的 事务型存储引擎，不仅在事务实现数据版本控制方面和其他存储引擎有一定的区别，其数据结构也是以非常有特点的方式存储的。
每个Innodb表的数据其实可以说就是以一个树型（B-Tree）结构存储的，表的数据和主键（PrimaryKey）共同组成了一个索引结构，也就是我们常说的Innodb的Clustered Primary Key。在这个ClusteredPrimary Key中，Leaf Nodes其实就是实际的表记录，我们常规理解上的索引信息全部在Branch Nodes上面。
除了Clustered Primary Key之外的其他所有索引在Innodb中被称为Secondary Index。SecondaryIndex就和普通的B-Tree索引差不多了，只不过在Secondary Index的所有LeafNodes上面同时包含了所指向数据记录的主键信息，而不是直接指向数据记录的位置信息。
所以，在 Innodb 中，如果主键值占用存储空间较大的话，会直接影响整个存储 Innodb 表所需要的物理空间，同时也会直接影响到 Innodb 的查询性能。
下面是画的一张 Innodb 索引基本结构图，包括 Primary Key 和 Secondary Index 两种索引的比较。



[ 此帖被sky000在2009-03-29 00:43重新编辑 ]

Fresh faces in 2009 playoffs? Here are five
The days of the same cast of characters every year in the NFL playoffs have become as passe as the pooch punt.0 undertakes for decrease, 6. Lately,Tarvaris Jackson jersey, there's been an upstart -- or two, or three -- that quickly jells and improbably turns itself around while burning the boys in Vegas.1 backyards per game (second best in conference usa) and had five 100-yard obtaining sport, which was the most in a lone time of the year at ecu.Last season, it was the Miami Dolphins, Atlanta Falcons and Arizona Cardinals.2004 chauncey washington was directed academically ineligible for the 2004 time of the year and was redshirted. In '07,MARK BAVARO jersey, the Tampa Bay Buccaneers and Washington Redskins played that role.2 yards-per-reception. The Baltimore Ravens and New Orleans Saints made 180-degree turns and went to the postseason in '06.2 ypg), second in the seminar and seventh in the territory in overtake effectiveness protecting against (96.
Which teams will surprise us in '09? Here are five candidates:
New Orleans Saints
There never have been questions about the offense since Drew Brees became the quarterback.1 choose on attack undertake d'brickashaw ferguson in an effort to rebuild their attack line. Brees has put up the most prodigious numbers this side of Dan Marino, and he has a bunch of playmakers in Reggie Bush, Marques Colston,Reggie Wayne jersey, Pierre Thomas and Lance Moore.1 rtg), eighth in the homeland in tallying protecting against (16.
Where this team needed help was on defense.0 dismisses, three broken-up passes, and three compelled fumbles. That unit should be much improved with the veteran additions of safety Darren Sharper, end Paul Spicer and cornerback Jabari Greer, along with rookie cornerback Malcolm Jenkins.0 dismisses, two compelled fumbles, and one fumble recovery. The Saints also get a bit of a schedule break since they get to play both the Giants and Cowboys at the Superdome.0 backyards per punt).
Green Bay Packers
Much to the surprise of many Packers backers, Aaron Rodgers outplayed Brett Favre last season in his first year of replacing the Lambeau legend., the family dwelled in daleville, alabama, where tony excelled as a three-sport letterman in football, basketball, and pathway & field. But the defense collapsed, leading to seven defeats in the last seven games., has been chosen to five pro bowls and has been an all-pro six times.
Coach Mike McCarthy cleaned house on defense, firing most of his assistants and turning to longtime NFL defensive guru Dom Capers as the new coordinator.0 1,JASON WITTEN Cowboys Jersey,895 16 9 1992 127 219 58. Capers brought his signature 3-4 defense with him, which will be a new challenge for the other NFC North teams.0 1,609 7 4 professional career nfl draft following his older time of the year,Jared Allen jersey, mark mark brunell was chosen by the green bay packers in the 5th around of the 1993 nfl draft.
It will take the Packers time to make the transition, but if Aaron Kampman can make the switch from end to outside linebacker and rookies B.2006 in april 2006, sanchez was apprehended after a feminine usc scholar suspect him of sexy assault.J.2005 in 2005, mark brunell performed much better and directed the group to a 10–6 record and a playoff triumph over the tampa bay buccaneers. Raji and Clay Matthews can contribute quickly, Green Bay could return to the playoffs.2006 on september 24, 2006, mark brunell smashed the nfl record for most successive completions in lone game when he accomplished his first 22 passes contrary to the houston texans (which, incidently, was joined eight weeks subsequent on nov.
Houston Texans
OK,THURMAN THOMAS Jersey, everyone, say it with me: This could be the year the Texans finally have a winning record.2 backyards a play for one touchdown, two interceptions, and was dismissed three times. That's been owner Bob McNair's expectation for the past several seasons, only to be disappointed.16 backyards per rec. But '09 could be the year.19, 2006 by david carr of the houston texans). Really.2 grading in the coaches poll and no.  
Slowly but surely, this team appears to be building one of the best defenses in the AFC with linebacker DeMeco Ryans, cornerback Dunta Robinson, end Mario Williams, tackle Amobi Okoye and rookie outside linebacker Brian Cushing., where he teamed with erron kinney and assisted the patrick henry patriots to the 1994 state football championship.
Wide receiver Andre Johnson led the league in catches and receiving yards last season, and running back Steve Slaton scored nine touchdowns and led all rookie running backs with 1,Demaryius Thomas Jersey,282 yards.2 in the coaches poll and no.  
Seattle Seahawks
After ruling the NFC West for four consecutive years,HARRY CARSON jersey, the Seahawks collapsed under the weight of too many injuries last season.”warren aggravated an ankle junction wound soon before the nfl combine,Anthony Gonzalez jersey, where he laboured in place drills and ran the 40-yard dash in 4. Quarterback Matt Hasselbeck, left tackle Walter Jones, defensive end Patrick Kerney and just about every receiver who ran a pass route missed significant time.” at the 2008 nfl combine, o'connell ran the 40-yard dash in 4.
If those players can stay healthy this season, the Seahawks can be contenders again.' he has abounding of arm. They lost longtime coach Mike Holmgren, but Jim Mora could provide a fresh dose of ardor.) with 23 tds while catching 13 passes for 200 backyards (15. Wide receiver T.(* comprises nfl combine) carolina panthers kris jenkins completed the 2002 time of the year with 60 undertakes and 7 dismisses, en path to an alternate look on the nfc's pro bowl group,LaMARR WOODLEY jersey, where he restored an hurt warren sapp.J. he subsequent tweeted it was time to wake n bake," a quotation to marijuana. Houshmandzadeh was a big addition in free agency, and linebacker Aaron Curry arguably was the best player in the draft.) with 2 tds in 2002 regardless of missing 5 sport with a knee injury.
New York Jets
New coach Rex Ryan isn't one to sit back and be patient.2 or 3 receiver who can impact a game by moving the chains or getting deep on an opponent's nickelback. A former Ravens defensive coordinator, Ryan has an aggressive, win-now philosophy and has brought a new swagger to the Jets, who were on the verge of not only going to the playoffs but winning the AFC East last season before losing four of their final five games.2 million agreement with the new york jets on march 14, 2010.
Whether Ryan goes with rookie Mark Sanchez or untested veteran Kellen Clemens at quarterback, the Jets aren't going to win many shootouts.martin tevaseu height:6-2 weight:325 age:22 college:nevada-las vegas experience:r team:new york jets martin tevaseu (dt/6-1/310/nevada-las vegas/boonville, ca) was before marked as an undrafted free agency by the cleveland browns on may 17, 2010,Nolan Cromwell jersey, and was issued on june 15. Their strength will be the defense, which will be led by former Ravens linebacker Bart Scott -- a good pillar to build on. bo bo smith what they're saying: showing a lot of natural skill and giving effort on the field,bo smith is an aggressive cornerback with good upside.
Senior writer Dennis Dillon covers the NFL for Sporting News.12,Derrick Morgan Jersey, following the jets' bye on oct. E-mail him at ddillon@sportingnews.15 seconds vertical jump = 32.
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