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实战4的理论部分，
由于个人并不是很深入的了解，自已也正在总结，会在后续为大家不上！
上面也啰嗦了半天，到底insert和save有什么区别呢？
在这里阐述一下下
insert函数不会改变变量值,而save函数把第一个变量的值改变了.为什么会这样呢,来看看它们的函数代码.
MongDB有个很方便的地方,只打函数的名字而不加括号,就能查看该函数的功能用法.
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| > db.user.insert
function ( obj , options, _allow_dot ){
if ( ! obj )
throw "no object passed to insert!";
var flags = 0;
var wc = undefined;
var allowDottedFields = false;
if ( options === undefined ) {
// do nothing
}
else if ( typeof(options) == 'object' ) {
if (options.ordered === undefined) {
//do nothing, like above
} else {
flags = options.ordered ? 0 : 1;
}
if (options.writeConcern)
wc = options.writeConcern;
if (options.allowdotted)
allowDottedFields = true;
} else {
flags = options;
}
// 1 = continueOnError, which is synonymous with unordered in the write commands/bulk-api
var ordered = ((flags & 1) == 0);
if (!wc)
wc = this.getWriteConcern();
var result = undefined;
var startTime = (typeof(_verboseShell) === 'undefined' ||
!_verboseShell) ? 0 : new Date().getTime();
if ( this.getMongo().writeMode() != "legacy" ) {
// Bit 1 of option flag is continueOnError. Bit 0 (stop on error) is the default.
var bulk = ordered ? this.initializeOrderedBulkOp() : this.initializeUnorderedBulkOp();
var isMultiInsert = Array.isArray(obj);
if (isMultiInsert) {
obj.forEach(function(doc) {
bulk.insert(doc);
});
}
else {
bulk.insert(obj);
}
try {
result = bulk.execute(wc);
if (!isMultiInsert)
result = result.toSingleResult();
}
catch( ex ) {
if ( ex instanceof BulkWriteError ) {
result = isMultiInsert ? ex.toResult() : ex.toSingleResult();
}
else if ( ex instanceof WriteCommandError ) {
result = isMultiInsert ? ex : ex.toSingleResult();
}
else {
// Other exceptions thrown
throw ex;
}
}
}
else {
if ( ! _allow_dot ) {
this._validateForStorage( obj );
}
if ( typeof( obj._id ) == "undefined" && ! Array.isArray( obj ) ){
var tmp = obj; // don't want to modify input
obj = {_id: new ObjectId()};
for (var key in tmp){
obj[key] = tmp[key];
}
}
this.getMongo().insert( this._fullName , obj, flags );
// enforce write concern, if required
if (wc)
result = this.runCommand("getLastError", wc instanceof WriteConcern ? wc.toJSON() : wc);
}
this._lastID = obj._id;
this._printExtraInfo("Inserted", startTime);
return result;
}
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| > db.user.insert
function ( obj , options, _allow_dot ){
if ( ! obj )
throw "no object passed to insert!";
var flags = 0;
var wc = undefined;
var allowDottedFields = false;
if ( options === undefined ) {
// do nothing
}
else if ( typeof(options) == 'object' ) {
if (options.ordered === undefined) {
//do nothing, like above
} else {
flags = options.ordered ? 0 : 1;
}
if (options.writeConcern)
wc = options.writeConcern;
if (options.allowdotted)
allowDottedFields = true;
} else {
flags = options;
}
// 1 = continueOnError, which is synonymous with unordered in the write commands/bulk-api
var ordered = ((flags & 1) == 0);
if (!wc)
wc = this.getWriteConcern();
var result = undefined;
var startTime = (typeof(_verboseShell) === 'undefined' ||
!_verboseShell) ? 0 : new Date().getTime();
if ( this.getMongo().writeMode() != "legacy" ) {
// Bit 1 of option flag is continueOnError. Bit 0 (stop on error) is the default.
var bulk = ordered ? this.initializeOrderedBulkOp() : this.initializeUnorderedBulkOp();
var isMultiInsert = Array.isArray(obj);
if (isMultiInsert) {
obj.forEach(function(doc) {
bulk.insert(doc);
});
}
else {
bulk.insert(obj);
}
try {
result = bulk.execute(wc);
if (!isMultiInsert)
result = result.toSingleResult();
}
catch( ex ) {
if ( ex instanceof BulkWriteError ) {
result = isMultiInsert ? ex.toResult() : ex.toSingleResult();
}
else if ( ex instanceof WriteCommandError ) {
result = isMultiInsert ? ex : ex.toSingleResult();
}
else {
// Other exceptions thrown
throw ex;
}
}
}
else {
if ( ! _allow_dot ) {
this._validateForStorage( obj );
}
if ( typeof( obj._id ) == "undefined" && ! Array.isArray( obj ) ){
var tmp = obj; // don't want to modify input
obj = {_id: new ObjectId()};
for (var key in tmp){
obj[key] = tmp[key];
}
}
this.getMongo().insert( this._fullName , obj, flags );
// enforce write concern, if required
if (wc)
result = this.runCommand("getLastError", wc instanceof WriteConcern ? wc.toJSON() : wc);
}
this._lastID = obj._id;
this._printExtraInfo("Inserted", startTime);
return result;
}
> db.user.save
function ( obj , opts ){
if ( obj == null )
throw "can't save a null";
if ( typeof( obj ) == "number" || typeof( obj) == "string" )
throw "can't save a number or string"
if ( typeof( obj._id ) == "undefined" ){
obj._id = new ObjectId();
return this.insert( obj , opts );
}
else {
return this.update( { _id : obj._id } , obj , Object.merge({ upsert:true }, opts));
}
}
>
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1
| 由上面可以看出,save函数实际就是根据参数条件,调用了insert或update函数.如果想插入的数据对象存在,insert函数会报错,而save函数是改变原来的对象;如果想插入的对象不存在,那么它们执行相同的插入操作.这里可以用几个字来概括它们两的区别,即所谓"有则改之,无则加之".
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发表于 2014-6-16 13:44:05
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