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20 | <h1 class="page-title">Source: loki-fs-structured-adapter.js</h1>
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28 | <article>
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29 | <pre class="prettyprint source linenums"><code>
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30 | /*
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31 | Loki (node) fs structured Adapter (need to require this script to instance and use it).
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32 |
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33 | This adapter will save database container and each collection to separate files and
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34 | save collection only if it is dirty. It is also designed to use a destructured serialization
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35 | method intended to lower the memory overhead of json serialization.
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36 |
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37 | This adapter utilizes ES6 generator/iterator functionality to stream output and
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38 | uses node linereader module to stream input. This should lower memory pressure
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39 | in addition to individual object serializations rather than loki's default deep object
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40 | serialization.
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41 | */
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42 |
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43 | (function (root, factory) {
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44 | if (typeof define === 'function' && define.amd) {
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45 | // AMD
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46 | define([], factory);
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47 | } else if (typeof exports === 'object') {
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48 | // Node, CommonJS-like
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49 | module.exports = factory();
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50 | } else {
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51 | // Browser globals (root is window)
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52 | root.LokiFsStructuredAdapter = factory();
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53 | }
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54 | }(this, function () {
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55 | return (function() {
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56 |
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57 | const fs = require('fs');
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58 | const readline = require('readline');
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59 | const stream = require('stream');
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60 |
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61 | /**
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62 | * Loki structured (node) filesystem adapter class.
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63 | * This class fulfills the loki 'reference' abstract adapter interface which can be applied to other storage methods.
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64 | *
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65 | * @constructor LokiFsStructuredAdapter
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66 | *
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67 | */
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68 | function LokiFsStructuredAdapter()
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69 | {
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70 | this.mode = "reference";
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71 | this.dbref = null;
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72 | this.dirtyPartitions = [];
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73 | }
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74 |
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75 | /**
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76 | * Generator for constructing lines for file streaming output of db container or collection.
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77 | *
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78 | * @param {object=} options - output format options for use externally to loki
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79 | * @param {int=} options.partition - can be used to only output an individual collection or db (-1)
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80 | *
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81 | * @returns {string|array} A custom, restructured aggregation of independent serializations.
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82 | * @memberof LokiFsStructuredAdapter
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83 | */
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84 | LokiFsStructuredAdapter.prototype.generateDestructured = function*(options) {
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85 | var idx, sidx;
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86 | var dbcopy;
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87 |
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88 | options = options || {};
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89 |
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90 | if (!options.hasOwnProperty("partition")) {
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91 | options.partition = -1;
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92 | }
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93 |
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94 | // if partition is -1 we will return database container with no data
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95 | if (options.partition === -1) {
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96 | // instantiate lightweight clone and remove its collection data
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97 | dbcopy = this.dbref.copy();
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98 |
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99 | for(idx=0; idx < dbcopy.collections.length; idx++) {
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100 | dbcopy.collections[idx].data = [];
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101 | }
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102 |
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103 | yield dbcopy.serialize({
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104 | serializationMethod: "normal"
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105 | });
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106 |
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107 | return;
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108 | }
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109 |
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110 | // 'partitioned' along with 'partition' of 0 or greater is a request for single collection serialization
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111 | if (options.partition >= 0) {
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112 | var doccount,
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113 | docidx;
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114 |
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115 | // dbref collections have all data so work against that
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116 | doccount = this.dbref.collections[options.partition].data.length;
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117 |
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118 | for(docidx=0; docidx<doccount; docidx++) {
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119 | yield JSON.stringify(this.dbref.collections[options.partition].data[docidx]);
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120 | }
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121 | }
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122 | };
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123 |
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124 | /**
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125 | * Loki persistence adapter interface function which outputs un-prototype db object reference to load from.
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126 | *
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127 | * @param {string} dbname - the name of the database to retrieve.
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128 | * @param {function} callback - callback should accept string param containing db object reference.
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129 | * @memberof LokiFsStructuredAdapter
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130 | */
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131 | LokiFsStructuredAdapter.prototype.loadDatabase = function(dbname, callback)
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132 | {
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133 | var instream = fs.createReadStream(dbname);
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134 | var outstream = new stream();
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135 | var rl = readline.createInterface(instream, outstream);
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136 | var self=this;
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137 |
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138 | this.dbref = null;
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139 |
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140 | // first, load db container component
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141 | rl.on('line', function(line) {
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142 | // it should single JSON object (a one line file)
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143 | if (self.dbref === null && line !== "") {
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144 | self.dbref = JSON.parse(line);
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145 | }
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146 | });
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147 |
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148 | // when that is done, examine its collection array to sequence loading each
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149 | rl.on('close', function() {
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150 | if (self.dbref.collections.length > 0) {
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151 | self.loadNextCollection(dbname, 0, function() {
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152 | callback(self.dbref);
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153 | });
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154 | }
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155 | });
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156 | };
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157 |
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158 | /**
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159 | * Recursive function to chain loading of each collection one at a time.
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160 | * If at some point i can determine how to make async driven generator, this may be converted to generator.
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161 | *
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162 | * @param {string} dbname - the name to give the serialized database within the catalog.
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163 | * @param {int} collectionIndex - the ordinal position of the collection to load.
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164 | * @param {function} callback - callback to pass to next invocation or to call when done
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165 | * @memberof LokiFsStructuredAdapter
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166 | */
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167 | LokiFsStructuredAdapter.prototype.loadNextCollection = function(dbname, collectionIndex, callback) {
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168 | var instream = fs.createReadStream(dbname + "." + collectionIndex);
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169 | var outstream = new stream();
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170 | var rl = readline.createInterface(instream, outstream);
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171 | var self=this,
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172 | obj;
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173 |
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174 | rl.on('line', function (line) {
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175 | if (line !== "") {
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176 | obj = JSON.parse(line);
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177 | self.dbref.collections[collectionIndex].data.push(obj);
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178 | }
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179 | });
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180 |
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181 | rl.on('close', function (line) {
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182 | instream = null;
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183 | outstream = null;
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184 | rl = null;
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185 | obj = null;
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186 |
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187 | // if there are more collections, load the next one
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188 | if (++collectionIndex < self.dbref.collections.length) {
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189 | self.loadNextCollection(dbname, collectionIndex, callback);
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190 | }
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191 | // otherwise we are done, callback to loadDatabase so it can return the new db object representation.
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192 | else {
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193 | callback();
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194 | }
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195 | });
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196 | };
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197 |
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198 | /**
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199 | * Generator for yielding sequence of dirty partition indices to iterate.
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200 | *
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201 | * @memberof LokiFsStructuredAdapter
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202 | */
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203 | LokiFsStructuredAdapter.prototype.getPartition = function*() {
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204 | var idx,
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205 | clen = this.dbref.collections.length;
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206 |
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207 | // since database container (partition -1) doesn't have dirty flag at db level, always save
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208 | yield -1;
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209 |
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210 | // yield list of dirty partitions for iterateration
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211 | for(idx=0; idx<clen; idx++) {
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212 | if (this.dbref.collections[idx].dirty) {
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213 | yield idx;
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214 | }
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215 | }
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216 | };
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217 |
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218 | /**
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219 | * Loki reference adapter interface function. Saves structured json via loki database object reference.
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220 | *
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221 | * @param {string} dbname - the name to give the serialized database within the catalog.
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222 | * @param {object} dbref - the loki database object reference to save.
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223 | * @param {function} callback - callback passed obj.success with true or false
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224 | * @memberof LokiFsStructuredAdapter
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225 | */
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226 | LokiFsStructuredAdapter.prototype.exportDatabase = function(dbname, dbref, callback)
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227 | {
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228 | var idx;
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229 |
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230 | this.dbref = dbref;
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231 |
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232 | // create (dirty) partition generator/iterator
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233 | var pi = this.getPartition();
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234 |
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235 | this.saveNextPartition(dbname, pi, function() {
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236 | callback(null);
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237 | });
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238 |
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239 | };
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240 |
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241 | /**
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242 | * Utility method for queueing one save at a time
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243 | */
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244 | LokiFsStructuredAdapter.prototype.saveNextPartition = function(dbname, pi, callback) {
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245 | var li;
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246 | var filename;
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247 | var self = this;
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248 | var pinext = pi.next();
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249 |
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250 | if (pinext.done) {
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251 | callback();
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252 | return;
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253 | }
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254 |
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255 | // db container (partition -1) uses just dbname for filename,
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256 | // otherwise append collection array index to filename
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257 | filename = dbname + ((pinext.value === -1)?"":("." + pinext.value));
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258 |
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259 | var wstream = fs.createWriteStream(filename);
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260 | //wstream.on('finish', function() {
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261 | wstream.on('close', function() {
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262 | self.saveNextPartition(dbname, pi, callback);
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263 | });
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264 |
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265 | li = this.generateDestructured({ partition: pinext.value });
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266 |
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267 | // iterate each of the lines generated by generateDestructured()
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268 | for(var outline of li) {
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269 | wstream.write(outline + "\n");
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270 | }
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271 |
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272 | wstream.end();
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273 | };
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274 |
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275 | return LokiFsStructuredAdapter;
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276 |
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277 | }());
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278 | }));
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279 | </code></pre>
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280 | </article>
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281 | </section>
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282 |
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283 |
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284 |
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285 |
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286 | </div>
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287 |
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288 | <nav>
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289 | <h2><a href="index.html">Home</a></h2><h3>Classes</h3><ul><li><a href="Collection.html">Collection</a></li><li><a href="DynamicView.html">DynamicView</a></li><li><a href="Loki.html">Loki</a></li><li><a href="LokiEventEmitter.html">LokiEventEmitter</a></li><li><a href="LokiFsAdapter.html">LokiFsAdapter</a></li><li><a href="LokiFsStructuredAdapter.html">LokiFsStructuredAdapter</a></li><li><a href="LokiIndexedAdapter.html">LokiIndexedAdapter</a></li><li><a href="LokiLocalStorageAdapter.html">LokiLocalStorageAdapter</a></li><li><a href="LokiMemoryAdapter.html">LokiMemoryAdapter</a></li><li><a href="LokiPartitioningAdapter.html">LokiPartitioningAdapter</a></li><li><a href="Resultset.html">Resultset</a></li></ul><h3>Tutorials</h3><ul><li><a href="tutorial-Autoupdating Collections.html">Autoupdating Collections</a></li><li><a href="tutorial-Changes API.html">Changes API</a></li><li><a href="tutorial-Collection Transforms.html">Collection Transforms</a></li><li><a href="tutorial-Indexing and Query performance.html">Indexing and Query performance</a></li><li><a href="tutorial-Loki Angular.html">Loki Angular</a></li><li><a href="tutorial-Persistence Adapters.html">Persistence Adapters</a></li><li><a href="tutorial-Query Examples.html">Query Examples</a></li></ul>
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