1 <?xml version="1.0" encoding="UTF-8"?>
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2 <chapter xml:id="data_models_and_access" xmlns="http://docbook.org/ns/docbook" version="5.0" xml:lang="EN"
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3 xmlns:xi="http://www.w3.org/2001/XInclude" xmlns:xlink="http://www.w3.org/1999/xlink">
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5 <title>Evergreen Data Models and Access</title>
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7 <abstract id="DM_abstract">
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8 <simpara>This chapter was taken from Dan Scott's <emphasis>Developer Workshop</emphasis>, February 2010.</simpara>
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10 <section id="exploring_database_schema">
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11 <title>Exploring the Database Schema</title>
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12 <simpara>The database schema is tied pretty tightly to PostgreSQL. Although PostgreSQL<indexterm><primary>databases</primary><secondary>PostgreSQL</secondary></indexterm>
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13 adheres closely to ANSI SQL standards, the use of schemas, SQL functions<indexterm><primary>ANSI</primary></indexterm>
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14 implemented in both <systemitem>plpgsql</systemitem> and <systemitem>plperl</systemitem>, and PostgreSQL’s native full-text
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15 search would make it… challenging… to port to other database platforms.</simpara>
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16 <simpara>A few common PostgreSQL interfaces for poking around the schema and
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17 manipulating data are:</simpara>
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21 psql (the command line client)<indexterm><primary>databases</primary><secondary>PostgreSQL</secondary><tertiery>psql</tertiery></indexterm>
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26 pgadminIII (a GUI client).<indexterm><primary>databases</primary><secondary>PostgreSQL</secondary><tertiery>pgadminIII</tertiery></indexterm>
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30 <simpara>Or you can read through the source files in <filename class="directoy">Open-ILS/src/sql/Pg</filename>.</simpara>
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31 <simpara>Let’s take a quick tour through the schemas, pointing out some highlights
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32 and some key interdependencies:</simpara>
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36 actor.org_unit → asset.copy_location
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41 actor.usr → actor.card
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46 biblio.record_entry → asset.call_number → asset.copy
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51 config.metabib_field → metabib.*_field_entry
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55 This documentation also contains an Appendix for the Evergreen <xref linkend="databaseschema"/>.
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57 <section id="_database_access_methods">
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58 <title>Database access methods</title>
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59 <simpara>You could use direct access to the database via Perl DBI, JDBC, etc,
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60 but Evergreen offers several database CRUD services for
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61 creating / retrieving / updating / deleting data. These avoid tying
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62 you too tightly to the current database schema and they funnel database
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63 access through the same mechanism, rather than tying up connections
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64 with other interfaces.</simpara>
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66 <section id="_evergreen_interface_definition_language_idl">
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67 <title>Evergreen Interface Definition Language (IDL)</title>
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68 <simpara>Defines properties and required permissions for Evergreen classes.
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69 To reduce network overhead, a given object is identified via a
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70 class-hint and serialized as a JSON array of properties (no named properties).</simpara>
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71 <simpara>As of 1.6, fields will be serialized in the order in which they appear
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72 in the IDL definition file, and the is_new / is_changed / is_deleted
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73 properties are automatically added. This has greatly reduced the size of
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74 the <literal>fm_IDL.xml</literal> file and makes DRY people happier :)</simpara>
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78 … oils_persist:readonly tells us, if true, that the data lives in the database, but is pulled from the SELECT statement defined in the <oils_persist:source_definition> child element
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82 <simplesect id="_idl_basic_example_config_language_map">
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83 <title>IDL basic example (config.language_map)</title>
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84 <programlisting language="xml" linenumbering="unnumbered">
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85 <class id="clm" controller="open-ils.cstore open-ils.pcrud"
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86 oils_obj:fieldmapper="config::language_map"
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87 oils_persist:tablename="config.language_map"
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88 reporter:label="Language Map" oils_persist:field_safe="true"> <co id="dmCO5-1"/> <co id="dmCO5-2"/> <co id="dmCO5-3"/> <co id="dmCO5-4"/>
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89 <fields oils_persist:primary="code" oils_persist:sequence=""> <co id="dmCO5-5"/>
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90 <field reporter:label="Language Code" name="code"
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91 reporter:selector="value" reporter:datatype="text"/> <co id="dmCO5-6"/>
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92 <field reporter:label="Language" name="value"
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93 reporter:datatype="text" oils_persist:i18n="true"/> <co id="dmCO5-7"/>
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96 <permacrud xmlns="http://open-ils.org/spec/opensrf/IDL/permacrud/v1"> <co id="dmCO5-8"/>
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98 <create global_required="true" permission="CREATE_MARC_CODE"> <co id="dmCO5-9"/>
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99 <retrieve global_required="true"
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100 permission="CREATE_MARC_CODE UPDATE_MARC_CODE DELETE_MARC_CODE">
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101 <update global_required="true" permission="UPDATE_MARC_CODE">
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102 <delete global_required="true" permission="DELETE_MARC_CODE">
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108 <callout arearefs="dmCO5-1">
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110 The <literal>class</literal> element defines the attributes and permissions for classes,
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111 and relationships between classes.
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116 The <literal>id</literal> attribute on the <literal>class</literal> element defines the class hint that is
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117 used everywhere in Evergreen.
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122 The <literal>controller</literal> attribute defines the OpenSRF
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123 services that provide access to the data for the class objects.
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128 <callout arearefs="dmCO5-2">
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130 The <literal>oils_obj::fieldmapper</literal> attribute defines the name of the class that
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131 is generated by <literal>OpenILS::Utils::Fieldmapper</literal>.
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134 <callout arearefs="dmCO5-3">
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136 The <literal>oils_persist:tablename</literal> attribute defines the name of the table
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137 that contains the data for the class objects.
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140 <callout arearefs="dmCO5-4">
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142 The reporter interface uses <literal>reporter:label</literal> attribute values in
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143 the source list to provide meaningful class and attribute names. The
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144 <literal>open-ils.fielder</literal> service generates a set of methods that provide direct
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145 access to the classes for which <literal>oils_persist:field_safe</literal> is <literal>true</literal>. For
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150 srfsh# request open-ils.fielder open-ils.fielder.clm.atomic \
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151 {"query":{"code":{"=":"eng"}}}
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162 <callout arearefs="dmCO5-5">
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164 The <literal>fields</literal> element defines the list of fields for the class.
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169 The <literal>oils_persist:primary</literal> attribute defines the column that acts as
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170 the primary key for the table.
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175 The <literal>oils_persist:sequence</literal> attribute holds the name of the database
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181 <callout arearefs="dmCO5-6">
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183 Each <literal>field</literal> element defines one property of the class.
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188 The <literal>name</literal> attribute defines the getter/setter method name for the field.
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193 The <literal>reporter:label</literal> attribute defines the attribute name as used in
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194 the reporter interface.
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199 The <literal>reporter:selector</literal> attribute defines the field used in the reporter
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200 filter interface to provide a selectable list. This gives the user a more
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201 meaningful access point than the raw numeric ID or abstract code.
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206 The <literal>reporter:datatype</literal> attribute defines the type of data held by
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207 this property for the purposes of the reporter.
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212 <callout arearefs="dmCO5-7">
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214 The <literal>oils_persist:i18n</literal> attribute, when <literal>true</literal>, means that
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215 translated values for the field’s contents may be accessible in
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219 <callout arearefs="dmCO5-8">
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221 The <literal>permacrud</literal> element defines the permissions (if any) required
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222 to <emphasis role="strong">c</emphasis>reate, <emphasis role="strong">r</emphasis>etrieve, <emphasis role="strong">u</emphasis>pdate,
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223 and <emphasis role="strong">d</emphasis>elete data for this
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224 class. <literal>open-ils.permacrud</literal> must be defined as a controller for the class
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225 for the permissions to be applied.
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228 <callout arearefs="dmCO5-9">
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230 Each action requires one or more <literal>permission</literal> values that the
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231 user must possess to perform the action.
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236 If the <literal>global_required</literal> attribute is <literal>true</literal>, then the user must
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237 have been granted that permission globally (depth = 0) to perform
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243 The <literal>context_field</literal> attribute denotes the <literal><field></literal> that identifies
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244 the org_unit at which the user must have the pertinent permission.
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249 An action element may contain a <literal><context_field></literal> element that
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250 defines the linked class (identified by the <literal>link</literal> attribute) and
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251 the field in the linked class that identifies the org_unit where
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252 the permission must be held.
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257 If the <literal><context_field></literal> element contains a <literal>jump</literal> attribute,
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258 then it defines a link to a link to a class with a field identifying
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259 the org_unit where the permission must be held.
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268 <simplesect id="_reporter_data_types_and_their_possible_values">
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269 <title>Reporter data types and their possible values</title>
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273 <literal>bool</literal>: Boolean <literal>true</literal> or <literal>false</literal>
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278 <literal>id</literal>: ID of the row in the database
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283 <literal>int</literal>: integer value
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288 <literal>interval</literal>: PostgreSQL time interval
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293 <literal>link</literal>: link to another class, as defined in the <literal><links></literal>
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294 element of the class definition
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299 <literal>money</literal>: currency amount
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304 <literal>org_unit</literal>: list of org_units
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309 <literal>text</literal>: text value
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314 <literal>timestamp</literal>: PostgreSQL timestamp
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319 <simplesect id="_idl_example_with_linked_fields_actor_workstation">
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320 <title>IDL example with linked fields (actor.workstation)</title>
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321 <simpara>Just as tables often include columns with foreign keys that point
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322 to values stored in the column of a different table, IDL classes
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323 can contain fields that link to fields in other classes. The <literal><links></literal>
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324 element defines which fields link to fields in other classes, and
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325 the nature of the relationship:</simpara>
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326 <programlisting language="xml" linenumbering="unnumbered">
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327 <class id="aws" controller="open-ils.cstore"
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328 oils_obj:fieldmapper="actor::workstation"
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329 oils_persist:tablename="actor.workstation"
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330 reporter:label="Workstation">
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331 <fields oils_persist:primary="id"
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332 oils_persist:sequence="actor.workstation_id_seq">
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333 <field reporter:label="Workstation ID" name="id"
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334 reporter:datatype="id"/>
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335 <field reporter:label="Workstation Name" name="name"
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336 reporter:datatype="text"/>
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337 <field reporter:label="Owning Library" name="owning_lib"
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338 reporter:datatype="org_unit"/>
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339 <field reporter:label="Circulations" name="circulations"
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340 oils_persist:virtual="true" reporter:datatype="link"/> <co id="dmCO6-1"/>
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342 <links> <co id="dmCO6-2"/>
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343 <link field="owning_lib" reltype="has_a" key="id"
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344 map="" class="aou"/> <co id="dmCO6-3"/>
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345 <link field="circulations" reltype="has_many" key="workstation"
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346 map="" class="circ"/>
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347 <link field="circulation_checkins" reltype="has_many"
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348 key="checkin_workstation" map="" class="circ"/>
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353 <callout arearefs="dmCO6-1">
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355 This field includes an <literal>oils_persist:virtual</literal> attribute with the value of
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356 <literal>true</literal>, meaning that the linked class <literal>circ</literal> is a virtual class.
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359 <callout arearefs="dmCO6-2">
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361 The <literal><links></literal> element contains 0 or more <literal><link></literal> elements.
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364 <callout arearefs="dmCO6-3">
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366 Each <literal><link></literal> element defines the field (<literal>field</literal>) that links to a different
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367 class (<literal>class</literal>), the relationship (<literal>rel_type</literal>) between this field and the target
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368 field (<literal>key</literal>). If the field in this class links to a virtual class, the (<literal>map</literal>)
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369 attribute defines the field in the target class that returns a list of matching
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370 objects for each object in this class.
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376 <section id="open_ils_cstore_literal_data_access_interfaces">
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377 <title><literal>open-ils.cstore</literal> data access interfaces</title>
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378 <simpara>For each class documented in the IDL, the <literal>open-ils.cstore</literal> service
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379 automatically generates a set of data access methods, based on the
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380 <literal>oils_persist:tablename</literal> class attribute.</simpara>
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381 <simpara>For example, for the class hint <literal>clm</literal>, cstore generates the following
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382 methods with the <literal>config.language_map</literal> qualifer:</simpara>
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386 <literal>open-ils.cstore.direct.config.language_map.id_list {"code" { "like": "e%" } }</literal>
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388 <simpara>Retrieves a list composed only of the IDs that match the query.</simpara>
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392 <literal>open-ils.cstore.direct.config.language_map.retrieve "eng"</literal>
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394 <simpara>Retrieves the object that matches a specific ID.</simpara>
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398 <literal>open-ils.cstore.direct.config.language_map.search {"code" : "eng"}</literal>
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400 <simpara>Retrieves a list of objects that match the query.</simpara>
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404 <literal>open-ils.cstore.direct.config.language_map.create <_object_></literal>
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406 <simpara>Creates a new object from the passed in object.</simpara>
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410 <literal>open-ils.cstore.direct.config.language_map.update <_object_></literal>
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412 <simpara>Updates the object that has been passed in.</simpara>
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416 <literal>open-ils.cstore.direct.config.language_map.delete "eng"</literal>
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418 <simpara>Deletes the object that matches the query.</simpara>
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422 <section id="_open_ils_pcrud_data_access_interfaces">
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423 <title>open-ils.pcrud data access interfaces</title>
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424 <simpara>For each class documented in the IDL, the <literal>open-ils.pcrud</literal> service
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425 automatically generates a set of data access methods, based on the
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426 <literal>oils_persist:tablename</literal> class attribute.</simpara>
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427 <simpara>For example, for the class hint <literal>clm</literal>, <literal>open-ils.pcrud</literal> generates the following
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428 methods that parallel the <literal>open-ils.cstore</literal> interface:</simpara>
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432 <literal>open-ils.pcrud.id_list.clm <_authtoken_>, { "code": { "like": "e%" } }</literal>
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437 <literal>open-ils.pcrud.retrieve.clm <_authtoken_>, "eng"</literal>
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442 <literal>open-ils.pcrud.search.clm <_authtoken_>, { "code": "eng" }</literal>
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447 <literal>open-ils.pcrud.create.clm <_authtoken_>, <_object_></literal>
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452 <literal>open-ils.pcrud.update.clm <_authtoken_>, <_object_></literal>
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457 <literal>open-ils.pcrud.delete.clm <_authtoken_>, "eng"</literal>
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462 <section id="_transaction_and_savepoint_control">
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463 <title>Transaction and savepoint control</title>
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464 <simpara>Both <literal>open-ils.cstore</literal> and <literal>open-ils.pcrud</literal> enable you to control database transactions
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465 to ensure that a set of operations either all succeed, or all fail,
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466 atomically:</simpara>
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470 <literal>open-ils.cstore.transaction.begin</literal>
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475 <literal>open-ils.cstore.transaction.commit</literal>
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480 <literal>open-ils.cstore.transaction.rollback</literal>
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485 <literal>open-ils.pcrud.transaction.begin</literal>
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490 <literal>open-ils.pcrud.transaction.commit</literal>
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495 <literal>open-ils.pcrud.transaction.rollback</literal>
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499 <simpara>At a more granular level, <literal>open-ils.cstore</literal> and <literal>open-ils.pcrud</literal> enable you to set database
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500 savepoints to ensure that a set of operations either all succeed, or all
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501 fail, atomically, within a given transaction:</simpara>
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505 <literal>open-ils.cstore.savepoint.begin</literal>
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510 <literal>open-ils.cstore.savepoint.commit</literal>
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515 <literal>open-ils.cstore.savepoint.rollback</literal>
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520 <literal>open-ils.pcrud.savepoint.begin</literal>
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525 <literal>open-ils.pcrud.savepoint.commit</literal>
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530 <literal>open-ils.pcrud.savepoint.rollback</literal>
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534 <simpara>Transactions and savepoints must be performed within a stateful
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535 connection to the <literal>open-ils.cstore</literal> and <literal>open-ils.pcrud</literal> services.
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536 In <literal>srfsh</literal>, you can open a stateful connection using the <literal>open</literal>
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537 command, and then close the stateful connection using the <literal>close</literal>
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538 command - for example:</simpara>
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539 <screen>srfsh# open open-ils.cstore
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540 ... perform various transaction-related work
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541 srfsh# close open-ils.cstore</screen>
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542 <simplesect id="_json_queries">
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543 <title>JSON Queries</title>
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544 <simpara>Beyond simply retrieving objects by their ID using the <literal>\*.retrieve</literal>
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545 methods, you can issue queries against the <literal>\*.delete</literal> and <literal>\*.search</literal>
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546 methods using JSON to filter results with simple or complex search
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547 conditions.</simpara>
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548 <simpara>For example, to generate a list of barcodes that are held in a
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549 copy location that allows holds and is visible in the OPAC:</simpara>
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550 <programlisting language="sh" linenumbering="unnumbered">
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551 srfsh# request open-ils.cstore open-ils.cstore.json_query <co id="dmCO7-1"/>
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552 {"select": {"acp":["barcode"], "acpl":["name"]}, <co id="dmCO7-2"/>
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553 "from": {"acp":"acpl"}, <co id="dmCO7-3"/>
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554 "where": [ <co id="dmCO7-4"/>
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555 {"+acpl": "holdable"}, <co id="dmCO7-5"/>
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556 {"+acpl": "opac_visible"} <co id="dmCO7-6"/>
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560 "barcode":"BARCODE1",
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565 "barcode":"BARCODE2",
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570 <callout arearefs="dmCO7-1">
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572 Invoke the <literal>json_query</literal> service.
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575 <callout arearefs="dmCO7-2">
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577 Select the <literal>barcode</literal> field from the <literal>acp</literal> class and the <literal>name</literal>
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578 field from the <literal>acpl</literal> class.
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581 <callout arearefs="dmCO7-3">
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583 Join the <literal>acp</literal> class to the <literal>acpl</literal> class based on the linked field
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584 defined in the IDL.
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587 <callout arearefs="dmCO7-4">
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589 Add a <literal>where</literal> clause to filter the results. We have more than one
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590 condition beginning with the same key, so we wrap the conditions inside
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594 <callout arearefs="dmCO7-5">
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596 The first condition tests whether the boolean value of the <literal>holdable</literal>
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597 field on the <literal>acpl</literal> class is true.
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600 <callout arearefs="dmCO7-6">
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602 The second condition tests whether the boolean value of the
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603 <literal>opac_visible</literal> field on the <literal>acpl</literal> class is true.
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607 <simpara>For thorough coverage of the breadth of support offered by JSON
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608 query syntax, see <ulink url="http://open-ils.org/dokuwiki/doku.php?id=documentation:technical:jsontutorial">JSON Queries: A Tutorial</ulink>.</simpara>
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610 <simplesect id="_fleshing_linked_objects">
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611 <title>Fleshing linked objects</title>
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612 <simpara>A simplistic approach to retrieving a set of objects that are linked to
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613 an object that you are retrieving - for example, a set of call numbers
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614 linked to the barcodes that a given user has borrowed - would be to:
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615 1. Retrieve the list of circulation objects (<literal>circ</literal> class)
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616 for a given user (<literal>usr</literal> class).
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617 2. For each circulation object, look up the target copy (<literal>target_copy</literal>
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618 field, linked to the <literal>acp</literal> class).
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619 3. For each copy, look up the call number for that copy (<literal>call_number</literal>
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620 field, linked to the <literal>acn</literal> class).</simpara>
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621 <simpara>However, this would result in potentially hundreds of round-trip
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622 queries from the client to the server. Even with low-latency connections,
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623 the network overhead would be considerable. So, built into the <literal>open-ils.cstore</literal> and
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624 <literal>open-ils.pcrud</literal> access methods is the ability to <emphasis>flesh</emphasis> linked fields -
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625 that is, rather than return an identifier to a given linked field,
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626 the method can return the entire object as part of the initial response.</simpara>
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627 <simpara>Most of the interfaces that return class instances from the IDL offer the
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628 ability to flesh returned fields. For example, the
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629 <literal>open-ils.cstore.direct.\*.retrieve</literal> methods allow you to specify a
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630 JSON structure defining the fields you wish to flesh in the returned object.</simpara>
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631 <formalpara><title>Fleshing fields in objects returned by <literal>open-ils.cstore</literal></title><para>
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632 <programlisting language="sh" linenumbering="unnumbered">
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633 srfsh# request open-ils.cstore open-ils.cstore.direct.asset.copy.retrieve 1, \
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635 "flesh": 1, <co id="dmCO8-1"/>
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636 "flesh_fields": { <co id="dmCO8-2"/>
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637 "acp": ["location"]
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641 </para></formalpara>
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643 <callout arearefs="dmCO8-1">
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645 The <literal>flesh</literal> argument is the depth at which objects should be fleshed.
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646 For example, to flesh out a field that links to another object that includes
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647 a field that links to another object, you would specify a depth of 2.
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650 <callout arearefs="dmCO8-2">
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652 The <literal>flesh_fields</literal> argument contains a list of objects with the fields
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653 to flesh for each object.
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657 <simpara>Let’s flesh things a little deeper. In addition to the copy location,
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658 let’s also flesh the call number attached to the copy, and then flesh
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659 the bibliographic record attached to the call number.</simpara>
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660 <formalpara><title>Fleshing fields in fields of objects returned by <literal>open-ils.cstore</literal></title><para>
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661 <programlisting language="java" linenumbering="unnumbered">
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662 request open-ils.cstore open-ils.cstore.direct.asset.copy.retrieve 1, \
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666 "acp": ["location", "call_number"],
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671 </para></formalpara>
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674 <section id="_adding_an_idl_entry_for_resolverresolver">
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675 <title>Adding an IDL entry for ResolverResolver</title>
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676 <simpara>Most OpenSRF methods in Evergreen define their object interface in the
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677 IDL. Without an entry in the IDL, the prospective caller of a given
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678 method is forced to either call the method and inspect the returned
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679 contents, or read the source to work out the structure of the JSON
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680 payload. At this stage of the tutorial, we have not defined an entry
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681 in the IDL to represent the object returned by the
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682 <literal>open-ils.resolver.resolve_holdings</literal> method. It is time to complete
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683 that task.</simpara>
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684 <simpara>The <literal>open-ils.resolver</literal> service is unlike many of the other classes
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685 defined in the IDL because its data is not stored in the Evergreen
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686 database. Instead, the data is requested from an external Web service
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687 and only temporarily cached in <literal>memcached</literal>. Fortunately, the IDL
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688 enables us to represent this kind of class by setting the
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689 <literal>oils_persist:virtual</literal> class attribute to <literal>true</literal>.</simpara>
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690 <simpara>So, let’s add an entry to the IDL for the <literal>open-ils.resolver.resolve_holdings</literal>
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692 <programlisting language="xml" linenumbering="unnumbered"></programlisting>
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693 <simpara>And let’s make <literal>ResolverResolver.pm</literal> return an array composed of our new
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694 <literal>rhr</literal> classes rather than raw JSON objects:</simpara>
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695 <programlisting language="perl" linenumbering="unnumbered"></programlisting>
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696 <simpara>Once we add the new entry to the IDL and copy the revised <literal>ResolverResolver.pm</literal>
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697 Perl module to <literal>/openils/lib/perl5/OpenILS/Application/</literal>, we need to:</simpara>
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698 <orderedlist numeration="arabic">
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701 Copy the updated IDL to both the <literal>/openils/conf/</literal> and
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702 <literal>/openils/var/web/reports/</literal> directories. The Dojo approach to
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703 parsing the IDL uses the IDL stored in the reports directory.
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708 Restart the Perl services to make the new IDL visible to the services
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709 and refresh the <literal>open-ils.resolver</literal> implementation
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714 Rerun <filename>/openils/bin/autogen.sh</filename> to regenerate the JavaScript versions<indexterm><primary>autogen</primary></indexterm>
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715 of the IDL required by the HTTP translator and gateway.
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719 <simpara>We also need to adjust our JavaScript client to use the nifty new<indexterm><primary>JavaScript</primary></indexterm>
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720 objects that <literal>open-ils.resolver.resolve_holdings</literal> now returns.
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721 The best approach is to use the support in Evergreen’s Dojo extensions<indexterm><primary>Dojo toolkit</primary></indexterm>
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722 to generate the JavaScript classes directly from the IDL XML file.</simpara>
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723 <formalpara><title>Accessing classes defined in the IDL via Fieldmapper</title><para>
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724 <programlisting language="html" linenumbering="unnumbered"></programlisting>
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725 </para></formalpara>
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727 <callout arearefs="">
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729 Load the Dojo core.
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732 <callout arearefs="">
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734 <literal>fieldmapper.AutoIDL</literal> reads <filename>/openils/var/reports/fm_IDL.xml</filename> to
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735 generate a list of class properties.
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738 <callout arearefs="">
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740 <literal>fieldmapper.dojoData</literal> seems to provide a store for Evergreen data
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744 <callout arearefs="">
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746 <literal>fieldmapper.Fieldmapper</literal> converts the list of class properties into
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750 <callout arearefs="">
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752 <literal>fieldmapper.standardRequest</literal> invokes an OpenSRF method and returns
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753 an array of objects.
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756 <callout arearefs="">
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758 The first argument to <literal>fieldmapper.standardRequest</literal> is an array
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759 containing the OpenSRF service name and method name.
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762 <callout arearefs="">
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764 The second argument to <literal>fieldmapper.standardRequest</literal> is an array
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765 containing the arguments to pass to the OpenSRF method.
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768 <callout arearefs="">
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770 As Fieldmapper has instantiated the returned objects based on their
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771 class hints, we can invoke getter/setter methods on the objects.
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