Editing API:EPrints/Database (section)

===Searching, caching and object retrieval===
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====cache_exp====

 $searchexp = $db-&gt;cache_exp( $cacheid )
Return the serialised search of a the cached search with <tt>$cacheid</tt>. Return <tt>undef</tt> if the <tt>$cacheid</tt> is invalid or expired.

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====cache====

 $cacheid = $db-&gt;cache( $searchexp, $dataset, $srctable, [$order], [$list] )
Create a cache of the specified search expression from the SQL table <tt>$srctable</tt>.

If <tt>$order</tt> is set then the cache is ordered by the specified fields.  For example <tt>-year/title</tt> orders by year (descending). Records with  the same year are ordered by title.

If <tt>$srctable</tt> is set to <tt>LIST</tt> then order is ignored and the list  of IDs is taken from the array reference <tt>$list</tt>.

If <tt>$srctable</tt> is set to <tt>ALL</tt> every matching record from $dataset  is added to the cache, optionally ordered by <tt>$order</tt>.

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====cache_table====

 $tablename = $db-&gt;cache_table( $id )
Return the name of the SQL table used to store the cache with <tt>$id</tt>.

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====cache_userid====

 $userid = $db-&gt;cache_userid( $id )
Returns the <tt>userid</tt> associated with the cache with <tt>$id</tt> if that  cache exists.

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====get_cachemap====

 $cachemap = $db-&gt;get_cachemap( $id )
Return the cachemap with $&lt;id&gt;.

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====search====

 $ids = $db-&gt;search( $keyfield, $tables, $conditions, [ $main_table_alias ] )
Return a reference to an array of <tt>$keyfield</tt> IDs - the results of  the search specified by <tt>$conditions</tt> across the tables specified in  the <tt>$tables</tt> hash where keys are tables aliases and values are table  names. 

If no <tt>$main_table_alias</tt> is specified then <tt>M</tt> is assumed. 

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====drop_cache====

 $db-&gt;drop_cache( $id )
Remove the cached search with the given <tt>$id</tt>.

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====from_cache====

 $items = $db-&gt;from_cache( $dataset, $cacheid, [ $offset, $count, $justids ] )
Return a reference to an array containing all the items from the given  <tt>$dataset</tt> that have IDs in the cache specified by <tt>$cacheid</tt>. The  cache may be specified either by ID or serialised search expression. 

<tt>$offset</tt> is an offset from the start of the cache and <tt>$count</tt> is  the number of records to return.

If <tt>$justids</tt> is <tt>true</tt> then it returns just a reference to an array  of the record IDs and not the objects themselves.

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====drop_orphan_cache_tables====

 $c = $db-&gt;drop_orphan_cache_tables
Drop tables called <tt>cacheXXX</tt> where <tt>XXX</tt> is an integer. Returns the  number of cache tables dropped.

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<!-- Pod2Wiki=item_get_single -->
====get_single====

 $obj = $db-&gt;get_single( $dataset, $id )
Return a single &lt;EPrints::DataObj&gt; from the given <tt>$dataset</tt> with primary key set to <tt>$id</tt>.

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<!-- Pod2Wiki=item_get_all -->
====get_all====

 $items = $db-&gt;get_all( $dataset )
Returns a reference to an array with all the &lt;EPrints::DataObj&gt;s from  the given <tt>$dataset</tt>.

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====get_cache_ids====

 @ids = $db-&gt;get_cache_ids( $dataset, $cachemap, $offset, $count )
Returns a list of <tt>$count</tt> IDs from <tt>$cache_id</tt> starting at  <tt>$offset</tt> and in the order in the <tt>$cachemap</tt>.

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<!-- Pod2Wiki=item_get_dataobjs -->
====get_dataobjs====

 @dataobjs = $db-&gt;get_dataobjs( $dataset, [ $id, $id, ... ] )
Retrieves the records in <tt>$dataset</tt> with the given <tt>$id</tt>(s). If an  <tt>$id</tt> doesn't exist in the database it will be ignored.

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====get_values====

 $values = $db-&gt;get_values( $field, $dataset )
Return a reference to an array of all the distinct values of the  [[API:EPrints/MetaField|EPrints::MetaField]] <tt>$field</tt> for the <tt>$dataset</tt> specified.

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====sort_values====

 $values = $db-&gt;sort_values( $field, $values, [ $langid ] )
Sorts and returns the list of <tt>$values</tt> using the database.

<tt>$field</tt> is used to get the order value for each value. <tt>$langid</tt>  (or $session-&gt;get_langid if unset) is used to determine the database  collation to use when sorting the resulting order values.

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<!-- Pod2Wiki=item_get_ids_by_field_values -->
====get_ids_by_field_values====

 $ids = $db-&gt;get_ids_by_field_values( $field, $dataset, [ %opts ] )
Return a reference to a hash table where the keys are specified  <tt>$datasets</tt>'s <tt>$field</tt> value IDs and the values are references to  arrays of IDs.

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<!-- Pod2Wiki=item_dequeue_events -->
====dequeue_events====

 @events = $db-&gt;dequeue_events( $n )
Attempt to dequeue upto <tt>$n</tt> events. May return between <tt>0</tt> and  <tt>$n</tt> events depending on parallel processes and how many events are  remaining in the queue.

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<!-- Pod2Wiki=item_ci_lookup -->
====ci_lookup====

 $value = $db-&gt;ci_lookup( $field, $value )
This is a hacky method to support case-insensitive lookup for usernames, emails, etc.  It returns the actual case-sensitive version of <tt>$value</tt> if there is a case-insensitive match for the <tt>$field</tt>.

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