An update that doesn't change a document's underlying size can be done in-place, without moving the document.
An update which does change a document's size forces MongoDB to move the document and update indexes, which is slower.
MongoDB can add extra padding to new documents which can allow in-place updates even when the size changes.
$inc an int doesn't usually increase a document's size since the field type usually remains the same.
Using $push to add a new embedded document is good example of a document changing size.
Analysis of past updates is used to determine what % of a document's size should be added as padding.
db.unicorns.insert({name:'sporkles',vampires:10})
db.unicorns.stats().paddingFactor
1// $inc doesn't increase a document's size
db.unicorns.update({name:'sporkles'},{$inc:{vampires:10}})
db.unicorns.stats().paddingFactor
1// add a new field
db.unicorns.update({name:'sporkles'},{$set:{zombies:2}})
db.unicorns.stats().paddingFactor
1.59// compact added in 2.0, must repairDatabase in previous versions
db.unicorns.compact()
db.unicorns.stats().paddingFactor
1
"But the grooms, or 'bettos,' as the Japanese call them, are not the only ones who indulge in tattooing. You will see many of the 'sendos,' or boat-coolies, thus marked, but in a less degree than the bettos. Perhaps it is because the grooms are obliged to run so much, and consequently wish to lay aside all garments. As they must wear something, they have their skins decorated in this way, and thus have a suit of clothing always about them. Joe Johnston's shattered army was at Jackson, about forty-five miles to northward; beleaguered Vicksburg was in the Northwest, a trifle farther away; Natchez lay southwest, still more distant; and nearly twice as far in the south was our heartbroken New Orleans. We had paused to recuperate our animals, and there was a rumor that we were to get new clothing. Anyhow we had rags with honor, and a right to make as much noise as we chose. "Nonsense, my dear fellow. Now let me open your eyes. Behold the great force of a man who is gifted with second sight. Where did you get those notes? Was it not on the same evening as the murder?" "Oh, nothing," came the reply. "Only I was so silly as to place the wrong end of my cigarette in my mouth and burnt my lips. What's tuberose?" Reviewing these mechanical conditions, we may at once see sufficient reasons for the platen movement of planing machines; and that it would be objectionable, if not impossible, to add a traversing or cutting action to tools already supported through the medium of eight joints. To traverse for cutting would require a moving gib joint in place of the bolted one, between the standards and main frame, leading to a complication of joints and movements quite impracticable. And disadvantaged aye begins the strife. We have already seen how this fundamental division is applied to the universe as a whole. But our philosopher is not content with classifying the phenomena as he finds360 them; he attempts to demonstrate the necessity of their dual existence; and in so doing is guilty of something very like a vicious circle. For, after proving from the terrestrial movements that there must be an eternal movement to keep them going, he now assumes the revolving aether, and argues that there must be a motionless solid centre for it to revolve round, although a geometrical axis would have served the purpose equally well. By a still more palpable fallacy, he proceeds to show that a body whose tendency is towards the centre, must, in the nature of things, be opposed by another body whose tendency is towards the circumference. In order to fill up the interval created by this opposition, two intermediate bodies are required, and thus we get the four elements—earth, water, air, and fire. These, again, are resolved into the antithetical couples, dry and wet, hot and cold, the possible combinations of which, by twos, give us the four elements once more. Earth is dry and cold, water cold and wet, air wet and hot, fire hot and dry; each adjacent pair having a quality in common, and each element being characterized by the excess of a particular quality; earth is especially dry, water cold, air wet, and fire hot. The common centre of each antithesis is what Aristotle calls the First Matter, the mere abstract unformed possibility of existence. This matter always combines two qualities, and has the power of oscillating from one quality to another, but it cannot, as a rule, simultaneously exchange both for their opposites. Earth may pass into water, exchanging dry for wet, but not so readily into air, which would necessitate a double exchange at the same moment. 192 He helped her out. "I have drifted in a way," he went on to explain. "I left home when I was a mere boy, and the spirit of savagery and unrest laid hold of me. I can't break away. And I'm not even sure that I want to. You, I dare say, can't understand." Yet he felt so sure, for some reason, that she could that he[Pg 71] merely nodded his head when she said briefly, "I can." "Then, too," he went on, "there is something in the Indian character that strikes a responsive chord in me. I come of lawless stock myself. I was born in Sidney." Then he stopped short. What business was it of hers where he had been born? He had never seen fit to speak of it before. Nevertheless he intended that she should understand now. So he made it quite plain. "Sidney was a convict settlement, you know," he said deliberately, "and marriages were promiscuous. My grandfather was an officer who was best away from England. My grandmother poisoned her first husband. That is on my mother's side. On my father's side it was about as mixed." He leaned back, crossing his booted legs and running his fingers into his cartridge belt. His manner asked with a certain defiance, what she was going to do about it, or to think. "Naw; git out. Don't bother me with no questions, I tell you," impatiently said a man in citizen's clothes, who with arms outspread was signalling the switching engines. "'Tain't my business to give information to people. Got all I kin do to furnish brains for them bull-headed engineers. Go to that Quartermaster you see over there in uniform. The Government pays him for knowin' things. It don't me." As little Pete dropped to the ground, his nervous finger touched the trigger and his gun went off up in the air. The others took this as a cue, and banged away as rapidly as they could get their muskets off. "I am no master," Cadnan said wearily. "I am a slave." "The people know," Dodd said. "It's out. It's all out. About the slavery. Is that what you mean?" Cadnan peered at him, half-fearfully. "You are a master." One did not give orders to masters, or argue with them. "Why not? There's naun shameful in it. Munds's brother did it for twenty years. And think of the difference it'll m?ake to us—thirty pound or so a year, instead of the dead loss of Harry's keep and the wages of an extra man beside. I tell you, mother, I wur fair sick about the farm till I thought of this." "Ben, I swear I'm your true wife." Reuben started, and Pete awoke noisily. Harry was frightened and dropped his string, crying because he could not find it. The knock came again, and this time Pete crossed the room yawning, and opened the door. www.foline.com.cn congfresh.com.cn www.candice.net.cn www.fuyo.net.cn www.yuanziya.com.cn dahangjia.com.cn hashport.com.cn www.b012.com.cn www.ckiy.com.cn bjangel.com.cn