1.6/development/datamodelsandaccess.xml

   1 <?xml version="1.0" encoding="UTF-8"?>\r
   2 <chapter xml:id="data_models_and_access" xmlns="http://docbook.org/ns/docbook" version="5.0" xml:lang="EN"\r
   3     xmlns:xi="http://www.w3.org/2001/XInclude" xmlns:xlink="http://www.w3.org/1999/xlink">\r
   4         <chapterinfo>\r
   5         <title>Evergreen Data Models and Access</title>\r
   6         </chapterinfo>\r
   7                 <abstract id="DM_abstract">\r
   8                 <simpara>This chapter was taken from Dan Scott's <emphasis>Developer Workshop</emphasis>, February 2010.</simpara>\r
   9         </abstract>\r
  10         <section id="exploring_database_schema">\r
  11                 <title>Exploring the Database Schema</title>\r
  12                 <simpara>The database schema is tied pretty tightly to PostgreSQL. Although PostgreSQL\r
  13                 adheres closely to ANSI SQL standards, the use of schemas, SQL functions\r
  14                 implemented in both plpgsql and plperl, and PostgreSQL&#8217;s native full-text\r
  15                 search would make it&#8230; challenging&#8230; to port to other database platforms.</simpara>\r
  16                 <simpara>A few common PostgreSQL interfaces for poking around the schema and\r
  17                 manipulating data are:</simpara>\r
  18                 <itemizedlist>\r
  19                 <listitem>\r
  20                 <simpara>\r
  21                 psql (the command line client)\r
  22                 </simpara>\r
  23                 </listitem>\r
  24                 <listitem>\r
  25                 <simpara>\r
  26                 pgadminIII (a GUI client).\r
  27                 </simpara>\r
  28                 </listitem>\r
  29                 </itemizedlist>\r
  30                 <simpara>Or you can read through the source files in Open-ILS/src/sql/Pg.</simpara>\r
  31                 <simpara>Let&#8217;s take a quick tour through the schemas, pointing out some highlights\r
  32                 and some key interdependencies:</simpara>\r
  33                 <itemizedlist>\r
  34                 <listitem>\r
  35                 <simpara>\r
  36                 actor.org_unit &#8594; asset.copy_location\r
  37                 </simpara>\r
  38                 </listitem>\r
  39                 <listitem>\r
  40                 <simpara>\r
  41                 actor.usr &#8594; actor.card\r
  42                 </simpara>\r
  43                 </listitem>\r
  44                 <listitem>\r
  45                 <simpara>\r
  46                 biblio.record_entry &#8594; asset.call_number &#8594; asset.copy\r
  47                 </simpara>\r
  48                 </listitem>\r
  49                 <listitem>\r
  50                 <simpara>\r
  51                 config.metabib_field &#8594; metabib.*_field_entry\r
  52                 </simpara>\r
  53                 </listitem>\r
  54                 </itemizedlist>\r
  55                 This documentation also contains an Appendix for the Evergreen <xref linkend="databaseschema"/>.         \r
  56         </section>\r
  57         <section id="_database_access_methods">\r
  58                 <title>Database access methods</title>\r
  59                 <simpara>You could use direct access to the database via Perl DBI, JDBC, etc,\r
  60                 but Evergreen offers several database CRUD services for\r
  61                 creating / retrieving / updating / deleting data. These avoid tying\r
  62                 you too tightly to the current database schema and they funnel database\r
  63                 access through the same mechanism, rather than tying up connections\r
  64                 with other interfaces.</simpara>\r
  65         </section>\r
  66         <section id="_evergreen_interface_definition_language_idl">\r
  67                 <title>Evergreen Interface Definition Language (IDL)</title>\r
  68                 <simpara>Defines properties and required permissions for Evergreen classes.\r
  69                 To reduce network overhead, a given object is identified via a\r
  70                 class-hint and serialized as a JSON array of properties (no named properties).</simpara>\r
  71                 <simpara>As of 1.6, fields will be serialized in the order in which they appear\r
  72                 in the IDL definition file, and the is_new / is_changed / is_deleted\r
  73                 properties are automatically added. This has greatly reduced the size of\r
  74                 the <literal>fm_IDL.xml</literal> file and makes DRY people happier :)</simpara>\r
  75                 <itemizedlist>\r
  76                 <listitem>\r
  77                 <simpara>\r
  78                 &#8230; oils_persist:readonly tells us, if true, that the data lives in the database, but is pulled from the SELECT statement defined in the &lt;oils_persist:source_definition&gt; child element\r
  79                 </simpara>\r
  80                 </listitem>\r
  81                 </itemizedlist>\r
  82                 <simplesect id="_idl_basic_example_config_language_map">\r
  83                         <title>IDL basic example (config.language_map)</title>\r
  84                         <programlisting language="xml" linenumbering="unnumbered">&lt;class id="clm" controller="open-ils.cstore open-ils.pcrud"\r
  85                                 oils_obj:fieldmapper="config::language_map"\r
  86                                 oils_persist:tablename="config.language_map"\r
  87                                 reporter:label="Language Map" oils_persist:field_safe="true"&gt; <co id="dmCO5-1"/> <co id="dmCO5-2"/> <co id="dmCO5-3"/> <co id="dmCO5-4"/>\r
  88                             &lt;fields oils_persist:primary="code" oils_persist:sequence=""&gt;  <co id="dmCO5-5"/>\r
  89                                 &lt;field reporter:label="Language Code" name="code"\r
  90                                     reporter:selector="value" reporter:datatype="text"/&gt; <co id="dmCO5-6"/>\r
  91                                 &lt;field reporter:label="Language" name="value"\r
  92                                     reporter:datatype="text" oils_persist:i18n="true"/&gt; <co id="dmCO5-7"/>\r
  93                             &lt;/fields&gt;\r
  94                             &lt;links/&gt;\r
  95                             &lt;permacrud xmlns="http://open-ils.org/spec/opensrf/IDL/permacrud/v1"&gt; <co id="dmCO5-8"/>\r
  96                                 &lt;actions&gt;\r
  97                                     &lt;create global_required="true" permission="CREATE_MARC_CODE"&gt; <co id="dmCO5-9"/>\r
  98                                     &lt;retrieve global_required="true"\r
  99                                         permission="CREATE_MARC_CODE UPDATE_MARC_CODE DELETE_MARC_CODE"&gt;\r
 100                                     &lt;update global_required="true" permission="UPDATE_MARC_CODE"&gt;\r
 101                                     &lt;delete global_required="true" permission="DELETE_MARC_CODE"&gt;\r
 102                                 &lt;/actions&gt;\r
 103                             &lt;/permacrud&gt;\r
 104                         &lt;/class&gt;</programlisting>\r
 105                         <calloutlist>\r
 106                         <callout arearefs="dmCO5-1">\r
 107                         <simpara>\r
 108                         The <literal>class</literal> element defines the attributes and permissions for classes,\r
 109                         and relationships between classes.\r
 110                         </simpara>\r
 111                         <itemizedlist>\r
 112                         <listitem>\r
 113                         <simpara>\r
 114                         The <literal>id</literal> attribute on the <literal>class</literal> element defines the class hint that is\r
 115                         used everywhere in Evergreen.\r
 116                         </simpara>\r
 117                         </listitem>\r
 118                         <listitem>\r
 119                         <simpara>\r
 120                         The <literal>controller</literal> attribute defines the OpenSRF\r
 121                         services that provide access to the data for the class objects.\r
 122                         </simpara>\r
 123                         </listitem>\r
 124                         </itemizedlist>\r
 125                         </callout>\r
 126                         <callout arearefs="dmCO5-2">\r
 127                         <simpara>\r
 128                         The <literal>oils_obj::fieldmapper</literal> attribute defines the name of the class that\r
 129                         is generated by <literal>OpenILS::Utils::Fieldmapper</literal>.\r
 130                         </simpara>\r
 131                         </callout>\r
 132                         <callout arearefs="dmCO5-3">\r
 133                         <simpara>\r
 134                         The <literal>oils_persist:tablename</literal> attribute defines the name of the table\r
 135                         that contains the data for the class objects.\r
 136                         </simpara>\r
 137                         </callout>\r
 138                         <callout arearefs="dmCO5-4">\r
 139                         <simpara>\r
 140                         The reporter interface uses <literal>reporter:label</literal> attribute values in\r
 141                         the source list to provide meaningful class and attribute names. The\r
 142                         <literal>open-ils.fielder</literal> service generates a set of methods that provide direct\r
 143                         access to the classes for which <literal>oils_persist:field_safe</literal> is <literal>true</literal>. For\r
 144                         example,\r
 145                         </simpara>\r
 146                         <screen>srfsh# request open-ils.fielder open-ils.fielder.clm.atomic \\r
 147                             {"query":{"code":{"=":"eng"}}}\r
 148 \r
 149                         Received Data: [\r
 150                           {\r
 151                             "value":"English",\r
 152                             "code":"eng"\r
 153                           }\r
 154                         ]</screen>\r
 155                         </callout>\r
 156                         <callout arearefs="dmCO5-5">\r
 157                         <simpara>\r
 158                         The <literal>fields</literal> element defines the list of fields for the class.\r
 159                         </simpara>\r
 160                         <itemizedlist>\r
 161                         <listitem>\r
 162                         <simpara>\r
 163                         The <literal>oils_persist:primary</literal> attribute defines the column that acts as\r
 164                         the primary key for the table.\r
 165                         </simpara>\r
 166                         </listitem>\r
 167                         <listitem>\r
 168                         <simpara>\r
 169                         The <literal>oils_persist:sequence</literal> attribute holds the name of the database\r
 170                         sequence.\r
 171                         </simpara>\r
 172                         </listitem>\r
 173                         </itemizedlist>\r
 174                         </callout>\r
 175                         <callout arearefs="dmCO5-6">\r
 176                         <simpara>\r
 177                         Each <literal>field</literal> element defines one property of the class.\r
 178                         </simpara>\r
 179                         <itemizedlist>\r
 180                         <listitem>\r
 181                         <simpara>\r
 182                         The <literal>name</literal> attribute defines the getter/setter method name for the field.\r
 183                         </simpara>\r
 184                         </listitem>\r
 185                         <listitem>\r
 186                         <simpara>\r
 187                         The <literal>reporter:label</literal> attribute defines the attribute name as used in\r
 188                         the reporter interface.\r
 189                         </simpara>\r
 190                         </listitem>\r
 191                         <listitem>\r
 192                         <simpara>\r
 193                         The <literal>reporter:selector</literal> attribute defines the field used in the reporter\r
 194                         filter interface to provide a selectable list. This gives the user a more\r
 195                         meaningful access point than the raw numeric ID or abstract code.\r
 196                         </simpara>\r
 197                         </listitem>\r
 198                         <listitem>\r
 199                         <simpara>\r
 200                         The <literal>reporter:datatype</literal> attribute defines the type of data held by\r
 201                         this property for the purposes of the reporter.\r
 202                         </simpara>\r
 203                         </listitem>\r
 204                         </itemizedlist>\r
 205                         </callout>\r
 206                         <callout arearefs="dmCO5-7">\r
 207                         <simpara>\r
 208                         The <literal>oils_persist:i18n</literal> attribute, when <literal>true</literal>, means that\r
 209                         translated values for the field&#8217;s contents may be accessible in\r
 210                         different locales.\r
 211                         </simpara>\r
 212                         </callout>\r
 213                         <callout arearefs="dmCO5-8">\r
 214                         <simpara>\r
 215                         The <literal>permacrud</literal> element defines the permissions (if any) required\r
 216                         to <emphasis role="strong">c</emphasis>reate, <emphasis role="strong">r</emphasis>etrieve, <emphasis role="strong">u</emphasis>pdate, and <emphasis role="strong">d</emphasis>elete data for this\r
 217                         class. <literal>open-ils.permacrud</literal> must be defined as a controller for the class\r
 218                         for the permissions to be applied.\r
 219                         </simpara>\r
 220                         </callout>\r
 221                         <callout arearefs="dmCO5-9">\r
 222                         <simpara>\r
 223                         Each action requires one or more <literal>permission</literal> values that the\r
 224                         user must possess to perform the action.\r
 225                         </simpara>\r
 226                         <itemizedlist>\r
 227                         <listitem>\r
 228                         <simpara>\r
 229                         If the <literal>global_required</literal> attribute is <literal>true</literal>, then the user must\r
 230                         have been granted that permission globally (depth = 0) to perform\r
 231                         the action.\r
 232                         </simpara>\r
 233                         </listitem>\r
 234                         <listitem>\r
 235                         <simpara>\r
 236                         The <literal>context_field</literal> attribute denotes the <literal>&lt;field&gt;</literal> that identifies\r
 237                         the org_unit at which the user must have the pertinent permission.\r
 238                         </simpara>\r
 239                         </listitem>\r
 240                         <listitem>\r
 241                         <simpara>\r
 242                         An action element may contain a <literal>&lt;context_field&gt;</literal> element that\r
 243                         defines the linked class (identified by the <literal>link</literal> attribute) and\r
 244                         the field in the linked class that identifies the org_unit where\r
 245                         the permission must be held.\r
 246                         </simpara>\r
 247                         <itemizedlist>\r
 248                         <listitem>\r
 249                         <simpara>\r
 250                         If the <literal>&lt;context_field&gt;</literal> element contains a <literal>jump</literal> attribute,\r
 251                         then it defines a link to a link to a class with a field identifying\r
 252                         the org_unit where the permission must be held.\r
 253                         </simpara>\r
 254                         </listitem>\r
 255                         </itemizedlist>\r
 256                         </listitem>\r
 257                         </itemizedlist>\r
 258                         </callout>\r
 259                         </calloutlist>\r
 260                 </simplesect>\r
 261                 <simplesect id="_reporter_data_types_and_their_possible_values">\r
 262                         <title>Reporter data types and their possible values</title>\r
 263                         <itemizedlist>\r
 264                         <listitem>\r
 265                         <simpara>\r
 266                         <literal>bool</literal>: Boolean <literal>true</literal> or <literal>false</literal>\r
 267                         </simpara>\r
 268                         </listitem>\r
 269                         <listitem>\r
 270                         <simpara>\r
 271                         <literal>id</literal>: ID of the row in the database\r
 272                         </simpara>\r
 273                         </listitem>\r
 274                         <listitem>\r
 275                         <simpara>\r
 276                         <literal>int</literal>: integer value\r
 277                         </simpara>\r
 278                         </listitem>\r
 279                         <listitem>\r
 280                         <simpara>\r
 281                         <literal>interval</literal>: PostgreSQL time interval\r
 282                         </simpara>\r
 283                         </listitem>\r
 284                         <listitem>\r
 285                         <simpara>\r
 286                         <literal>link</literal>: link to another class, as defined in the <literal>&lt;links&gt;</literal>\r
 287                         element of the class definition\r
 288                         </simpara>\r
 289                         </listitem>\r
 290                         <listitem>\r
 291                         <simpara>\r
 292                         <literal>money</literal>: currency amount\r
 293                         </simpara>\r
 294                         </listitem>\r
 295                         <listitem>\r
 296                         <simpara>\r
 297                         <literal>org_unit</literal>: list of org_units\r
 298                         </simpara>\r
 299                         </listitem>\r
 300                         <listitem>\r
 301                         <simpara>\r
 302                         <literal>text</literal>: text value\r
 303                         </simpara>\r
 304                         </listitem>\r
 305                         <listitem>\r
 306                         <simpara>\r
 307                         <literal>timestamp</literal>: PostgreSQL timestamp\r
 308                         </simpara>\r
 309                         </listitem>\r
 310                         </itemizedlist>\r
 311                 </simplesect>\r
 312                 <simplesect id="_idl_example_with_linked_fields_actor_workstation">\r
 313                         <title>IDL example with linked fields (actor.workstation)</title>\r
 314                         <simpara>Just as tables often include columns with foreign keys that point\r
 315                         to values stored in the column of a different table, IDL classes\r
 316                         can contain fields that link to fields in other classes. The <literal>&lt;links&gt;</literal>\r
 317                         element defines which fields link to fields in other classes, and\r
 318                         the nature of the relationship:</simpara>\r
 319                         <programlisting language="xml" linenumbering="unnumbered">&lt;class id="aws" controller="open-ils.cstore"\r
 320                                 oils_obj:fieldmapper="actor::workstation"\r
 321                                 oils_persist:tablename="actor.workstation"\r
 322                                 reporter:label="Workstation"&gt;\r
 323                             &lt;fields oils_persist:primary="id"\r
 324                                     oils_persist:sequence="actor.workstation_id_seq"&gt;\r
 325                                 &lt;field reporter:label="Workstation ID" name="id"\r
 326                                         reporter:datatype="id"/&gt;\r
 327                                 &lt;field reporter:label="Workstation Name" name="name"\r
 328                                         reporter:datatype="text"/&gt;\r
 329                                 &lt;field reporter:label="Owning Library" name="owning_lib"\r
 330                                         reporter:datatype="org_unit"/&gt;\r
 331                                 &lt;field reporter:label="Circulations" name="circulations"\r
 332                                         oils_persist:virtual="true" reporter:datatype="link"/&gt; <co id="dmCO6-1"/>\r
 333                             &lt;/fields&gt;\r
 334                             &lt;links&gt;  <co id="dmCO6-2"/>\r
 335                                 &lt;link field="owning_lib" reltype="has_a" key="id"\r
 336                                         map="" class="aou"/&gt;  <co id="dmCO6-3"/>\r
 337                                 &lt;link field="circulations" reltype="has_many" key="workstation"\r
 338                                         map="" class="circ"/&gt;\r
 339                                 &lt;link field="circulation_checkins" reltype="has_many"\r
 340                                         key="checkin_workstation" map="" class="circ"/&gt;\r
 341                             &lt;/links&gt;\r
 342                         &lt;/class&gt;</programlisting>\r
 343                         <calloutlist>\r
 344                         <callout arearefs="dmCO6-1">\r
 345                         <simpara>\r
 346                         This field includes an <literal>oils_persist:virtual</literal> attribute with the value of\r
 347                         <literal>true</literal>, meaning that the linked class <literal>circ</literal> is a virtual class.\r
 348                         </simpara>\r
 349                         </callout>\r
 350                         <callout arearefs="dmCO6-2">\r
 351                         <simpara>\r
 352                         The <literal>&lt;links&gt;</literal> element contains 0 or more <literal>&lt;link&gt;</literal> elements.\r
 353                         </simpara>\r
 354                         </callout>\r
 355                         <callout arearefs="dmCO6-3">\r
 356                         <simpara>\r
 357                         Each <literal>&lt;link&gt;</literal> element defines the field (<literal>field</literal>) that links to a different\r
 358                         class (<literal>class</literal>), the relationship (<literal>rel_type</literal>) between this field and the target\r
 359                         field (<literal>key</literal>). If the field in this class links to a virtual class, the (<literal>map</literal>)\r
 360                         attribute defines the field in the target class that returns a list of matching\r
 361                         objects for each object in this class.\r
 362                         </simpara>\r
 363                         </callout>\r
 364                         </calloutlist>\r
 365                 </simplesect>\r
 366         </section>\r
 367         <section id="open_ils_cstore_literal_data_access_interfaces">\r
 368                 <title><literal>open-ils.cstore</literal> data access interfaces</title>\r
 369                 <simpara>For each class documented in the IDL, the <literal>open-ils.cstore</literal> service\r
 370                 automatically generates a set of data access methods, based on the\r
 371                 <literal>oils_persist:tablename</literal> class attribute.</simpara>\r
 372                 <simpara>For example, for the class hint <literal>clm</literal>, cstore generates the following\r
 373                 methods with the <literal>config.language_map</literal> qualifer:</simpara>\r
 374                 <itemizedlist>\r
 375                 <listitem>\r
 376                 <simpara>\r
 377                 <literal>open-ils.cstore.direct.config.language_map.id_list {"code" { "like": "e%" } }</literal>\r
 378                 </simpara>\r
 379                 <simpara>Retrieves a list composed only of the IDs that match the query.</simpara>\r
 380                 </listitem>\r
 381                 <listitem>\r
 382                 <simpara>\r
 383                 <literal>open-ils.cstore.direct.config.language_map.retrieve "eng"</literal>\r
 384                 </simpara>\r
 385                 <simpara>Retrieves the object that matches a specific ID.</simpara>\r
 386                 </listitem>\r
 387                 <listitem>\r
 388                 <simpara>\r
 389                 <literal>open-ils.cstore.direct.config.language_map.search {"code" : "eng"}</literal>\r
 390                 </simpara>\r
 391                 <simpara>Retrieves a list of objects that match the query.</simpara>\r
 392                 </listitem>\r
 393                 <listitem>\r
 394                 <simpara>\r
 395                 <literal>open-ils.cstore.direct.config.language_map.create &lt;_object_&gt;</literal>\r
 396                 </simpara>\r
 397                 <simpara>Creates a new object from the passed in object.</simpara>\r
 398                 </listitem>\r
 399                 <listitem>\r
 400                 <simpara>\r
 401                 <literal>open-ils.cstore.direct.config.language_map.update &lt;_object_&gt;</literal>\r
 402                 </simpara>\r
 403                 <simpara>Updates the object that has been passed in.</simpara>\r
 404                 </listitem>\r
 405                 <listitem>\r
 406                 <simpara>\r
 407                 <literal>open-ils.cstore.direct.config.language_map.delete "eng"</literal>\r
 408                 </simpara>\r
 409                 <simpara>Deletes the object that matches the query.</simpara>\r
 410                 </listitem>\r
 411                 </itemizedlist>\r
 412         </section>\r
 413         <section id="_open_ils_pcrud_data_access_interfaces">\r
 414                 <title>open-ils.pcrud data access interfaces</title>\r
 415                 <simpara>For each class documented in the IDL, the <literal>open-ils.pcrud</literal> service\r
 416                 automatically generates a set of data access methods, based on the\r
 417                 <literal>oils_persist:tablename</literal> class attribute.</simpara>\r
 418                 <simpara>For example, for the class hint <literal>clm</literal>, <literal>open-ils.pcrud</literal> generates the following\r
 419                 methods that parallel the <literal>open-ils.cstore</literal> interface:</simpara>\r
 420                 <itemizedlist>\r
 421                 <listitem>\r
 422                 <simpara>\r
 423                 <literal>open-ils.pcrud.id_list.clm &lt;_authtoken_&gt;, { "code": { "like": "e%" } }</literal>\r
 424                 </simpara>\r
 425                 </listitem>\r
 426                 <listitem>\r
 427                 <simpara>\r
 428                 <literal>open-ils.pcrud.retrieve.clm &lt;_authtoken_&gt;, "eng"</literal>\r
 429                 </simpara>\r
 430                 </listitem>\r
 431                 <listitem>\r
 432                 <simpara>\r
 433                 <literal>open-ils.pcrud.search.clm &lt;_authtoken_&gt;, { "code": "eng" }</literal>\r
 434                 </simpara>\r
 435                 </listitem>\r
 436                 <listitem>\r
 437                 <simpara>\r
 438                 <literal>open-ils.pcrud.create.clm &lt;_authtoken_&gt;, &lt;_object_&gt;</literal>\r
 439                 </simpara>\r
 440                 </listitem>\r
 441                 <listitem>\r
 442                 <simpara>\r
 443                 <literal>open-ils.pcrud.update.clm &lt;_authtoken_&gt;, &lt;_object_&gt;</literal>\r
 444                 </simpara>\r
 445                 </listitem>\r
 446                 <listitem>\r
 447                 <simpara>\r
 448                 <literal>open-ils.pcrud.delete.clm &lt;_authtoken_&gt;, "eng"</literal>\r
 449                 </simpara>\r
 450                 </listitem>\r
 451                 </itemizedlist>\r
 452         </section>\r
 453         <section id="_transaction_and_savepoint_control">\r
 454                 <title>Transaction and savepoint control</title>\r
 455                 <simpara>Both <literal>open-ils.cstore</literal> and <literal>open-ils.pcrud</literal> enable you to control database transactions\r
 456                 to ensure that a set of operations either all succeed, or all fail,\r
 457                 atomically:</simpara>\r
 458                 <itemizedlist>\r
 459                 <listitem>\r
 460                 <simpara>\r
 461                 <literal>open-ils.cstore.transaction.begin</literal>\r
 462                 </simpara>\r
 463                 </listitem>\r
 464                 <listitem>\r
 465                 <simpara>\r
 466                 <literal>open-ils.cstore.transaction.commit</literal>\r
 467                 </simpara>\r
 468                 </listitem>\r
 469                 <listitem>\r
 470                 <simpara>\r
 471                 <literal>open-ils.cstore.transaction.rollback</literal>\r
 472                 </simpara>\r
 473                 </listitem>\r
 474                 <listitem>\r
 475                 <simpara>\r
 476                 <literal>open-ils.pcrud.transaction.begin</literal>\r
 477                 </simpara>\r
 478                 </listitem>\r
 479                 <listitem>\r
 480                 <simpara>\r
 481                 <literal>open-ils.pcrud.transaction.commit</literal>\r
 482                 </simpara>\r
 483                 </listitem>\r
 484                 <listitem>\r
 485                 <simpara>\r
 486                 <literal>open-ils.pcrud.transaction.rollback</literal>\r
 487                 </simpara>\r
 488                 </listitem>\r
 489                 </itemizedlist>\r
 490                 <simpara>At a more granular level, <literal>open-ils.cstore</literal> and <literal>open-ils.pcrud</literal> enable you to set database\r
 491                 savepoints to ensure that a set of operations either all succeed, or all\r
 492                 fail, atomically, within a given transaction:</simpara>\r
 493                 <itemizedlist>\r
 494                 <listitem>\r
 495                 <simpara>\r
 496                 <literal>open-ils.cstore.savepoint.begin</literal>\r
 497                 </simpara>\r
 498                 </listitem>\r
 499                 <listitem>\r
 500                 <simpara>\r
 501                 <literal>open-ils.cstore.savepoint.commit</literal>\r
 502                 </simpara>\r
 503                 </listitem>\r
 504                 <listitem>\r
 505                 <simpara>\r
 506                 <literal>open-ils.cstore.savepoint.rollback</literal>\r
 507                 </simpara>\r
 508                 </listitem>\r
 509                 <listitem>\r
 510                 <simpara>\r
 511                 <literal>open-ils.pcrud.savepoint.begin</literal>\r
 512                 </simpara>\r
 513                 </listitem>\r
 514                 <listitem>\r
 515                 <simpara>\r
 516                 <literal>open-ils.pcrud.savepoint.commit</literal>\r
 517                 </simpara>\r
 518                 </listitem>\r
 519                 <listitem>\r
 520                 <simpara>\r
 521                 <literal>open-ils.pcrud.savepoint.rollback</literal>\r
 522                 </simpara>\r
 523                 </listitem>\r
 524                 </itemizedlist>\r
 525                 <simpara>Transactions and savepoints must be performed within a stateful\r
 526                 connection to the <literal>open-ils.cstore</literal> and <literal>open-ils.pcrud</literal> services.\r
 527                 In <literal>srfsh</literal>, you can open a stateful connection using the <literal>open</literal>\r
 528                 command, and then close the stateful connection using the <literal>close</literal>\r
 529                 command - for example:</simpara>\r
 530                 <screen>srfsh# open open-ils.cstore\r
 531                 ... perform various transaction-related work\r
 532                 srfsh# close open-ils.cstore</screen>\r
 533                 <simplesect id="_json_queries">\r
 534                         <title>JSON Queries</title>\r
 535                         <simpara>Beyond simply retrieving objects by their ID using the <literal>\*.retrieve</literal>\r
 536                         methods, you can issue queries against the <literal>\*.delete</literal> and <literal>\*.search</literal>\r
 537                         methods using JSON to filter results with simple or complex search\r
 538                         conditions.</simpara>\r
 539                         <simpara>For example, to generate a list of barcodes that are held in a\r
 540                         copy location that allows holds and is visible in the OPAC:</simpara>\r
 541                         <programlisting language="sh" linenumbering="unnumbered">srfsh# request open-ils.cstore open-ils.cstore.json_query  <co id="dmCO7-1"/>\r
 542                             {"select": {"acp":["barcode"], "acpl":["name"]}, <co id="dmCO7-2"/>\r
 543                              "from":   {"acp":"acpl"},   <co id="dmCO7-3"/>\r
 544                              "where":  [     <co id="dmCO7-4"/>\r
 545                                  {"+acpl": "holdable"},   <co id="dmCO7-5"/>\r
 546                                  {"+acpl": "opac_visible"}     <co id="dmCO7-6"/>\r
 547                              ]}\r
 548 \r
 549                         Received Data: {\r
 550                           "barcode":"BARCODE1",\r
 551                           "name":"Stacks"\r
 552                         }\r
 553 \r
 554                         Received Data: {\r
 555                           "barcode":"BARCODE2",\r
 556                           "name":"Stacks"\r
 557                         }</programlisting>\r
 558                         <calloutlist>\r
 559                         <callout arearefs="dmCO7-1">\r
 560                         <simpara>\r
 561                         Invoke the <literal>json_query</literal> service.\r
 562                         </simpara>\r
 563                         </callout>\r
 564                         <callout arearefs="dmCO7-2">\r
 565                         <simpara>\r
 566                         Select the <literal>barcode</literal> field from the <literal>acp</literal> class and the <literal>name</literal>\r
 567                         field from the <literal>acpl</literal> class.\r
 568                         </simpara>\r
 569                         </callout>\r
 570                         <callout arearefs="dmCO7-3">\r
 571                         <simpara>\r
 572                         Join the <literal>acp</literal> class to the <literal>acpl</literal> class based on the linked field\r
 573                         defined in the IDL.\r
 574                         </simpara>\r
 575                         </callout>\r
 576                         <callout arearefs="dmCO7-4">\r
 577                         <simpara>\r
 578                         Add a <literal>where</literal> clause to filter the results. We have more than one\r
 579                         condition beginning with the same key, so we wrap the conditions inside\r
 580                         an array.\r
 581                         </simpara>\r
 582                         </callout>\r
 583                         <callout arearefs="dmCO7-5">\r
 584                         <simpara>\r
 585                         The first condition tests whether the boolean value of the <literal>holdable</literal>\r
 586                         field on the <literal>acpl</literal> class is true.\r
 587                         </simpara>\r
 588                         </callout>\r
 589                         <callout arearefs="dmCO7-6">\r
 590                         <simpara>\r
 591                         The second condition tests whether the boolean value of the\r
 592                         <literal>opac_visible</literal> field on the <literal>acpl</literal> class is true.\r
 593                         </simpara>\r
 594                         </callout>\r
 595                         </calloutlist>\r
 596                         <simpara>For thorough coverage of the breadth of support offered by JSON\r
 597                         query syntax, see <ulink url="http://open-ils.org/dokuwiki/doku.php?id=documentation:technical:jsontutorial">JSON Queries: A Tutorial</ulink>.</simpara>\r
 598                 </simplesect>\r
 599                 <simplesect id="_fleshing_linked_objects">\r
 600                         <title>Fleshing linked objects</title>\r
 601                         <simpara>A simplistic approach to retrieving a set of objects that are linked to\r
 602                         an object that you are retrieving - for example, a set of call numbers\r
 603                         linked to the barcodes that a given user has borrowed - would be to:\r
 604                           1. Retrieve the list of circulation objects (<literal>circ</literal> class)\r
 605                         for a given user (<literal>usr</literal> class).\r
 606                           2. For each circulation object, look up the target copy (<literal>target_copy</literal>\r
 607                         field, linked to the <literal>acp</literal> class).\r
 608                           3. For each copy, look up the call number for that copy (<literal>call_number</literal>\r
 609                         field, linked to the <literal>acn</literal> class).</simpara>\r
 610                         <simpara>However, this would result in potentially hundreds of round-trip\r
 611                         queries from the client to the server. Even with low-latency connections,\r
 612                         the network overhead would be considerable. So, built into the <literal>open-ils.cstore</literal> and\r
 613                         <literal>open-ils.pcrud</literal> access methods is the ability to <emphasis>flesh</emphasis> linked fields -\r
 614                         that is, rather than return an identifier to a given linked field,\r
 615                         the method can return the entire object as part of the initial response.</simpara>\r
 616                         <simpara>Most of the interfaces that return class instances from the IDL offer the\r
 617                         ability to flesh returned fields. For example, the\r
 618                         <literal>open-ils.cstore.direct.\*.retrieve</literal> methods allow you to specify a\r
 619                         JSON structure defining the fields you wish to flesh in the returned object.</simpara>\r
 620                         <formalpara><title>Fleshing fields in objects returned by <literal>open-ils.cstore</literal></title><para>\r
 621                         <programlisting language="sh" linenumbering="unnumbered">srfsh# request open-ils.cstore open-ils.cstore.direct.asset.copy.retrieve 1, \\r
 622                             {\r
 623                                 "flesh": 1,    <co id="dmCO8-1"/>\r
 624                                 "flesh_fields": {   <co id="dmCO8-2"/>\r
 625                                     "acp": ["location"]\r
 626                                 }\r
 627                             }</programlisting>\r
 628                         </para></formalpara>\r
 629                         <calloutlist>\r
 630                         <callout arearefs="dmCO8-1">\r
 631                         <simpara>\r
 632                         The <literal>flesh</literal> argument is the depth at which objects should be fleshed.\r
 633                         For example, to flesh out a field that links to another object that includes\r
 634                         a field that links to another object, you would specify a depth of 2.\r
 635                         </simpara>\r
 636                         </callout>\r
 637                         <callout arearefs="dmCO8-2">\r
 638                         <simpara>\r
 639                         The <literal>flesh_fields</literal> argument contains a list of objects with the fields\r
 640                         to flesh for each object.\r
 641                         </simpara>\r
 642                         </callout>\r
 643                         </calloutlist>\r
 644                         <simpara>Let&#8217;s flesh things a little deeper. In addition to the copy location,\r
 645                         let&#8217;s also flesh the call number attached to the copy, and then flesh\r
 646                         the bibliographic record attached to the call number.</simpara>\r
 647                         <formalpara><title>Fleshing fields in fields of objects returned by <literal>open-ils.cstore</literal></title><para>\r
 648                         <programlisting language="java" linenumbering="unnumbered">request open-ils.cstore open-ils.cstore.direct.asset.copy.retrieve 1, \\r
 649                             {\r
 650                                 "flesh": 2,\r
 651                                 "flesh_fields": {\r
 652                                     "acp": ["location", "call_number"],\r
 653                                     "acn": ["record"]\r
 654                                  }\r
 655                             }</programlisting>\r
 656                         </para></formalpara>\r
 657                 </simplesect>\r
 658         </section>\r
 659         <section id="_adding_an_idl_entry_for_resolverresolver">\r
 660                 <title>Adding an IDL entry for ResolverResolver</title>\r
 661                 <simpara>Most OpenSRF methods in Evergreen define their object interface in the\r
 662                 IDL. Without an entry in the IDL, the prospective caller of a given\r
 663                 method is forced to either call the method and inspect the returned\r
 664                 contents, or read the source to work out the structure of the JSON\r
 665                 payload. At this stage of the tutorial, we have not defined an entry\r
 666                 in the IDL to represent the object returned by the\r
 667                 <literal>open-ils.resolver.resolve_holdings</literal> method. It is time to complete\r
 668                 that task.</simpara>\r
 669                 <simpara>The <literal>open-ils.resolver</literal> service is unlike many of the other classes\r
 670                 defined in the IDL because its data is not stored in the Evergreen\r
 671                 database. Instead, the data is requested from an external Web service\r
 672                 and only temporarily cached in <literal>memcached</literal>. Fortunately, the IDL\r
 673                 enables us to represent this kind of class by setting the\r
 674                 <literal>oils_persist:virtual</literal> class attribute to <literal>true</literal>.</simpara>\r
 675                 <simpara>So, let&#8217;s add an entry to the IDL for the <literal>open-ils.resolver.resolve_holdings</literal>\r
 676                 service:</simpara>\r
 677                 <programlisting language="xml" linenumbering="unnumbered"></programlisting>\r
 678                 <simpara>And let&#8217;s make <literal>ResolverResolver.pm</literal> return an array composed of our new\r
 679                 <literal>rhr</literal> classes rather than raw JSON objects:</simpara>\r
 680                 <programlisting language="perl" linenumbering="unnumbered"></programlisting>\r
 681                 <simpara>Once we add the new entry to the IDL and copy the revised <literal>ResolverResolver.pm</literal>\r
 682                 Perl module to <literal>/openils/lib/perl5/OpenILS/Application/</literal>, we need to:</simpara>\r
 683                 <orderedlist numeration="arabic">\r
 684                 <listitem>\r
 685                 <simpara>\r
 686                 Copy the updated IDL to both the <literal>/openils/conf/</literal> and\r
 687                 <literal>/openils/var/web/reports/</literal> directories. The Dojo approach to\r
 688                 parsing the IDL uses the IDL stored in the reports directory.\r
 689                 </simpara>\r
 690                 </listitem>\r
 691                 <listitem>\r
 692                 <simpara>\r
 693                 Restart the Perl services to make the new IDL visible to the services\r
 694                 and refresh the <literal>open-ils.resolver</literal> implementation\r
 695                 </simpara>\r
 696                 </listitem>\r
 697                 <listitem>\r
 698                 <simpara>\r
 699                 Rerun <literal>/openils/bin/autogen.sh</literal> to regenerate the JavaScript versions\r
 700                 of the IDL required by the HTTP translator and gateway.\r
 701                 </simpara>\r
 702                 </listitem>\r
 703                 </orderedlist>\r
 704                 <simpara>We also need to adjust our JavaScript client to use the nifty new\r
 705                 objects that <literal>open-ils.resolver.resolve_holdings</literal> now returns.\r
 706                 The best approach is to use the support in Evergreen&#8217;s Dojo extensions\r
 707                 to generate the JavaScript classes directly from the IDL XML file.</simpara>\r
 708                 <formalpara><title>Accessing classes defined in the IDL via Fieldmapper</title><para>\r
 709                 <programlisting language="html" linenumbering="unnumbered"></programlisting>\r
 710                 </para></formalpara>\r
 711                 <calloutlist>\r
 712                 <callout arearefs="">\r
 713                 <simpara>\r
 714                 Load the Dojo core.\r
 715                 </simpara>\r
 716                 </callout>\r
 717                 <callout arearefs="">\r
 718                 <simpara>\r
 719                 <literal>fieldmapper.AutoIDL</literal> reads <literal>/openils/var/reports/fm_IDL.xml</literal> to\r
 720                 generate a list of class properties.\r
 721                 </simpara>\r
 722                 </callout>\r
 723                 <callout arearefs="">\r
 724                 <simpara>\r
 725                 <literal>fieldmapper.dojoData</literal> seems to provide a store for Evergreen data\r
 726                 accessed via Dojo.\r
 727                 </simpara>\r
 728                 </callout>\r
 729                 <callout arearefs="">\r
 730                 <simpara>\r
 731                 <literal>fieldmapper.Fieldmapper</literal> converts the list of class properties into\r
 732                 actual classes.\r
 733                 </simpara>\r
 734                 </callout>\r
 735                 <callout arearefs="">\r
 736                 <simpara>\r
 737                 <literal>fieldmapper.standardRequest</literal> invokes an OpenSRF method and returns\r
 738                 an array of objects.\r
 739                 </simpara>\r
 740                 </callout>\r
 741                 <callout arearefs="">\r
 742                 <simpara>\r
 743                 The first argument to <literal>fieldmapper.standardRequest</literal> is an array\r
 744                 containing the OpenSRF service name and method name.\r
 745                 </simpara>\r
 746                 </callout>\r
 747                 <callout arearefs="">\r
 748                 <simpara>\r
 749                 The second argument to <literal>fieldmapper.standardRequest</literal> is an array\r
 750                 containing the arguments to pass to the OpenSRF method.\r
 751                 </simpara>\r
 752                 </callout>\r
 753                 <callout arearefs="">\r
 754                 <simpara>\r
 755                 As Fieldmapper has instantiated the returned objects based on their\r
 756                 class hints, we can invoke getter/setter methods on the objects.\r
 757                 </simpara>\r
 758                 </callout>\r
 759                 </calloutlist>\r
 760         </section>\r
 761         \r
 762 </chapter>\r