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126 lines
3.1 KiB
126 lines
3.1 KiB
/**
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* Manage access to data, be it to find, update or remove it
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*/
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var model = require('./model');
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/**
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* Create a new cursor for this collection
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* @param {Datastore} db - The datastore this cursor is bound to
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* @param {Query} query - The query this cursor will operate on
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* @param {Function} execDn - Handler to be executed after cursor has found the results and before the callback passed to find/findOne/update/remove
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*/
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function Cursor (db, query, execFn) {
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this.db = db;
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this.query = query || {};
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if (execFn) { this.execFn = execFn; }
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}
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/**
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* Set a limit to the number of results
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*/
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Cursor.prototype.limit = function(limit) {
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this._limit = limit;
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return this;
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};
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/**
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* Skip a the number of results
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*/
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Cursor.prototype.skip = function(skip) {
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this._skip = skip;
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return this;
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};
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/**
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* Sort results of the query
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* @Param {SortQuery} sortQuery - SortQuery is { field: order }, field can use the dot-notation, order is 1 for ascending and -1 for descending
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*/
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Cursor.prototype.sort = function(sortQuery) {
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this._sort = sortQuery;
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return this;
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};
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/**
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* Get all matching elements
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* Will return pointers to matched elements (shallow copies), returning full copies is the role of find or findOne
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* This is an internal function, use exec which uses the executor
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*
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* @param {Function} callback - Signature: err, results
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*/
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Cursor.prototype._exec = function(callback) {
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var candidates = this.db.getCandidates(this.query)
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, res = [], added = 0, skipped = 0, self = this
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, i, keys, key
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;
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try {
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for (i = 0; i < candidates.length; i += 1) {
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if (model.match(candidates[i], this.query)) {
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// If a sort is defined, wait for the results to be sorted before applying limit and skip
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if (!this._sort) {
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if (this._skip && this._skip > skipped) {
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skipped += 1;
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} else {
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res.push(candidates[i]);
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added += 1;
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if (this._limit && this._limit <= added) { break; }
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}
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} else {
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res.push(candidates[i]);
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}
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}
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}
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} catch (err) {
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return callback(err);
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}
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// Apply all sorts
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if (this._sort) {
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keys = Object.keys(this._sort);
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// Sorting
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var criteria = [];
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for (i = 0; i < keys.length; i++) {
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key = keys[i];
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criteria.push({ key: key, direction: self._sort[key] });
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}
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res.sort(function(a, b) {
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var criterion, compare, i;
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for (i = 0; i < criteria.length; i++) {
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criterion = criteria[i];
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compare = criterion.direction * model.compareThings(model.getDotValue(a, criterion.key), model.getDotValue(b, criterion.key));
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if (compare !== 0) {
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return compare;
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}
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}
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return 0;
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});
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// Applying limit and skip
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var limit = this._limit || res.length
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, skip = this._skip || 0;
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res = res.slice(skip, skip + limit);
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}
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if (this.execFn) {
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return this.execFn(null, res, callback);
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} else {
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return callback(null, res);
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}
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};
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Cursor.prototype.exec = function () {
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this.db.executor.push({ this: this, fn: this._exec, arguments: arguments });
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};
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// Interface
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module.exports = Cursor; |