From: Rick James Date: April 23 2012 6:54pm Subject: RE: Why does the limit use the early row lookup. List-Archive: http://lists.mysql.com/mysql/227233 Message-Id: <2E7DD7ADE53B044C8C8BCD9C5829E1EB1485A7D8E8@SP2-EX07VS01.ds.corp.yahoo.com> MIME-Version: 1.0 Content-Type: text/plain; charset="gb2312" Content-Transfer-Encoding: base64 SW5ub0RCIG9yIE15SVNBTT8NClBSSU1BUlkgS0VZIChpZCkgaXMgYSBzZXBhcmF0ZSBpbmRleCBp biBNeUlTQU0sIHNvIHNjYW5uaW5nIDEwMDAwMTAgcm93cyBpcyBmYXN0ZXIgdGhhbiBmb3IgSW5u b0RCLCB3aGVyZSB0aGUgUEsgaXMgImNsdXN0ZXJlZCIgd2l0aCB0aGUgZGF0YS4gIFRoYXQgaXMs IE15SVNBTSBzY2FucyBhIG5hcnJvdywgMi1jb2x1bW4sIGluZGV4IChpZCArIHBvaW50ZXIpOyBJ bm5vREIgc2NhbnMgd2lkZSByb3dzIChhbGwgY29sdW1ucykuDQoNClRoZXJlIGlzIG5vIHdheSB0 byBhdm9pZCBzY2FubmluZyAxMDAwMDEwIHJvd3Mgb2Ygc29tZXRoaW5nIChkYXRhIG9yIGluZGV4 KS4NCg0KSWYgeW91IGFyZSBkb2luZyBQYWdpbmF0aW9uIHZpYSBPRkZTRVQgYW5kIExJTUlUIC0t IERvbid0LiAgSW5zdGVhZCwgcmVtZW1iZXIgd2hlcmUgeW91ICJsZWZ0IG9mZiIuICAoTW9yZSBk ZXRhaWxzIHVwb24gcmVxdWVzdC4pDQoNCllvdSBjYW4gdHJpY2sgTXlTUUwgaW50byBkb2luZyAi bGF0ZSByb3cgbG9va3VwIiB2aWEgYSAic2VsZiBqb2luIjoNClNFTEVDVCBiLioNCiAgICBGUk9N IHRibCBhDQogICAgSk9JTiAoIFNFTEVDVCBpZCBGUk9NICB0YmwgT1JERVIgQlkgaWQgTElNSVQg MTAwMDAwMCwgMTApIGINCiAgICAgICAgT04gYS5pZCA9IGIuaWQNCg0KTWVhbndoaWxlLCBzZWUg aWYgaXQgaXMgYWxyZWFkeSBhIGZlYXR1cmUgcmVxdWVzdCBhdCBidWdzLm15c3FsLmNvbSAuICBJ ZiBub3QsIGFkZCBpdC4NCg0KUHJvYmFibHkgdGhlIG9wdGltaXphdGlvbiBuZWVkcyBoZXVyaXN0 aWNzIHRvIGRlY2lkZSB3aGljaCB3YXkgdG8gZ28uICBUaGUgY2hvaWNlIG9mIGVhcmx5IHZzIGxh dGUgbWF5IGRlcGVuZCBvbiBhbGwgb2YgdGhlc2U6DQogICogT0ZGU0VUDQogICogTElNSVQNCiAg KiBOdW1iZXIgb2Ygcm93cyBpbiB0aGUgdGFibGUNCiAgKiBXaWR0aCBvZiB0aGUgdGFibGUgdmVy c3VzIHdpZHRoIG9mIHRoZSBrZXkgaW52b2x2ZWQuDQoNCj4gLS0tLS1PcmlnaW5hbCBNZXNzYWdl LS0tLS0NCj4gRnJvbTog1cXWvrjVIFttYWlsdG86emhpZ2FuZ0BsZWp1LnNpbmEuY29tLmNuXQ0K PiBTZW50OiBUaHVyc2RheSwgQXByaWwgMTksIDIwMTIgNzozMCBQTQ0KPiBUbzogbXlzcWxAbGlz dHMubXlzcWwuY29tDQo+IFN1YmplY3Q6IFdoeSBkb2VzIHRoZSBsaW1pdCB1c2UgdGhlIGVhcmx5 IHJvdyBsb29rdXAuDQo+IA0KPiBEZWFyIGFsbDoNCj4gDQo+IEkgZW5jb3VudGVkIGEgcXVlc3Rp b24gdGhhdCB0aGUgbGltaXQgaXMgbm90IHVzZSBpbmRleCB0byBsb29rdXAgcm93DQo+IHdoZW4g SSBpc3N1ZSBhIHNxbC4NCj4gDQo+IFRoZW9yZXRpY2FsbHksIHRoZSBsb2NrIGlzIHVzZWQgd2hl biB0aGUgc3FsIHVwZGF0ZSB0YWJsZSBkYXRhIGFuZA0KPiB1cGRhdGUgdGFibGUgaW5kZXhlcywg SXQgZW5zdXJlcyB1cGRhdGluZyBkYXRhIGFuZCB1cGRhdGluZyBpbmRleGVzIGFyZQ0KPiBzeW5j aHJvbm91cy4NCj4gDQo+IFdoeSBkb2VzIHRoZSBsaW1pdCB1c2UgZWFybHkgcm93IGxvb2t1cCBi dXQgbm90IGxhdGUgcm93IGxvb2t1cD8NCj4gDQo+IEZvciBleGFtcGxlIDoNCj4gDQo+IENyZWF0 ZSB0YWJsZSB0ZXN0IChpZCBpbnQgcHJpbWFyeSBrZXksIG5hbWUgY2hhcigyMCkpOw0KPiANCj4g c2VsZWN0ICogZnJvbSB0ZXN0IG9yZGVyIGJ5IGlkIGxpbWl0IDEwMDAwMDAsIDEwLg0KPiANCj4g VGhlIGFib3ZlIHNxbCBpcyB2ZXJ5IHNsb3cgd2hlbiBvbmUgZmV0Y2ggY29sdW1uIGlzIG5vdCBp biB0aGUgaW5kZXhlcw0KPiBhbmQgdGhlIG9mZnNldCBpcyBtb3JlIHRoYW4gbWlsbGlvbi4NCj4g DQo+IFRoZSBhYm92ZSBzcWwgY291bnQgb2ZmIHRoZSAxMDAwMDEwIHJvd3MgYW5kIHJldHVybiB0 aGUgdG9wIDEwIHJvd3MuDQo+IA0KPiBCdXQgdGhlIHNxbDogc2VsZWN0IGlkIGZyb20gdGVzdCBv cmRlciBieSBpZCBsaW1pdCAxMDAwMDAwLCAxMCBpcyB2ZXJ5DQo+IGZhc3SjrGl0IHNraXBzIHRv IGNvdW50IG9mZiB0aGUgMTAwMDAwMCByb3dzIGJ5IHVzaW5nIGluZGV4ZXMsIGFuZA0KPiBjb3Vu dCBvZmYNCj4gMTAgcm93cyBvbmx5Lg0KPiANCj4gSSBkb26hr3Qga25vdyB0aGUgcmVhc29uLg0K PiANCj4gTXkgcG9pbnQgaXMgdGhhdCB0aGUgbGltaXQgY2FuIHVzZSBsYXRlIHJvdyBsb29rdXA6 IGxvb2t1cCByb3dzIGFmdGVyDQo+IGNoZWNraW5nIGluZGV4ZXMgdG8gb3B0aW1pemUgdGhlIHNl bGVjdCBzcGVlZC4NCj4gDQo+IEJ1dCB0aGUgbXlzcWwgb3B0aW1pemVyIGRvIGl0IHdpdGggdGhl IGVhcmx5IHJvdyBsb29rdXA6IGxvb2t1cCBhbGwNCj4gcm93cyBiZWZvcmUgY2hlY2tpbmcgaW5k ZXhlcyB3aGVuIHRoZSBvbmUgZmV0Y2ggY29sdW1uIGlzIG5vdCBpbiB0aGUNCj4gaW5kZXhlcy4N Cj4gDQo+IFRlbGwgbWUgd2h5Pw0KPiANCj4gVGhhbmtzDQo+IA0KPiANCj4gDQo+IFNpbmNlcmVs eSB5b3VycywNCj4gDQo+IFpoaWdhbmcgemhhbmcNCg0K