Editing API:EPrints/Database (section)

==METHODS==
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<!-- Pod2Wiki=head_database -->
===Database===
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<!-- Pod2Wiki=item_new -->
====new====

 $db = EPrints::Database-&gt;new( $repo, [ %opts ] )
Create a connection to the database.

Options:
  db_connect - Boolean. Also connect to the database (default: true).

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<!-- Pod2Wiki=item_create -->
====create====

 $db = $db-&gt;create( $username, $password )
Create and connect to a new database using user account <tt>$username</tt>  and <tt>$password</tt>.

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<!-- Pod2Wiki=item_build_connection_string -->
====build_connection_string====

 $dbstr = EPrints::Database::build_connection_string( %params )
Build the string to use to connect to the database via {{API:PodLink|file=DBI|package_name=DBI|section=|text=DBI}}.

Parameters:
 dbname - Database name (REQUIRED).
 dbdriver - Database driver (e.g. mysql, Oracle, pgsql, default: mysql).
 dbhost - Database host.  Assumes localhost if unset.
 dbport - Port to connect to database host.  Assumes default for driver if unset.
 dbsock - Socket file to connect to database through.

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<!-- Pod2Wiki=item_connect -->
====connect====

 $db-&gt;connect()
Connects to the database. 

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<!-- Pod2Wiki=item_disconnect -->
====disconnect====

 $db-&gt;disconnect()
Disconnects from the EPrints database. Should always be done before  any script exits.

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<!-- Pod2Wiki=item_set_debug -->
====set_debug====

 $db-&gt;set_debug( $boolean )
Set the SQL debug mode to <tt>true</tt> or <tt>false</tt>.

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<!-- Pod2Wiki=item_set_version -->
====set_version====

 $db-&gt;set_version( $versionid );
Set the version id table in the SQL database to the given <tt>versionid</tt> (used by the upgrade script).

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<!-- Pod2Wiki=item_get_version -->
====get_version====

 $version = $db-&gt;get_version
Returns the current database schema version. 

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<!-- Pod2Wiki=item_is_latest_version -->
====is_latest_version====

 $boolean = $db-&gt;is_latest_version
Return <tt>true</tt> if the SQL tables are in the correct configuration for this edition of eprints. Otherwise, <tt>false</tt>.

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<!-- Pod2Wiki=item_get_server_version -->
====get_server_version====

 $version = $db-&gt;get_server_version
Return the database server version.

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<!-- Pod2Wiki=item_get_default_charset -->
====get_default_charset====

 $charset = $db-&gt;get_default_charset
Return the character set to use.

Returns <tt>undef</tt> if character sets are unsupported.

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<!-- Pod2Wiki=item_get_default_collation -->
====get_default_collation====

 $collation = $db-&gt;get_default_collation( $lang )
Return the collation to use for language <tt>$lang</tt>.

Returns <tt>undef</tt> if collation is unsupported.

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<!-- Pod2Wiki=item_get_driver_name -->
====get_driver_name====

 $driver = $db-&gt;get_driver_name
Return the database driver name.

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<!-- Pod2Wiki=item_error -->
====error====

 $errstr = $db-&gt;error()
Return a string describing the last SQL error.

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<!-- Pod2Wiki=item_retry_error -->
====retry_error====

 $boolean = $db-&gt;retry_error()
Returns a boolean for whether the database error is a retry error.

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<!-- Pod2Wiki=item_duplicate_error -->
====duplicate_error====

 $boolean = $db-&gt;duplicate_error()
Returns a boolean for whether the database error is a duplicate error.

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<!-- Pod2Wiki=item_begin -->
====begin====

 $db-&gt;begin()
Begin a transaction.

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<!-- Pod2Wiki=item_commit -->
====commit====

 $db-&gt;commit()
Commit the previously begun transaction.

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<!-- Pod2Wiki=item_rollback -->
====rollback====

 $db-&gt;rollback()
Rollback the partially completed transaction.

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<!-- Pod2Wiki=item_type_info -->
====type_info====

 $type_info = $db-&gt;type_info( $data_type )
See {{API:PodLink|file=DBI|package_name=DBI|section=type_info|text=DBI/type_info}}.

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<!-- Pod2Wiki=item_get_column_type -->
====get_column_type====

 $real_type = $db-&gt;get_column_type( $name, $data_type, $not_null, [ $length, $scale, %opts ] )
Returns a SQL column definition for <tt>$name</tt> of type <tt>$type</tt>, usually something like:

  $name $type($length,$scale) [ NOT NULL ]
  
If <tt>$not_null</tt> is <tt>true</tt> column will be set to <tt>NOT NULL</tt>.

<tt>$length</tt> and <tt>$scale</tt> control the maximum lengths of character or decimal types (see below).

Other options available to refine the column definition:

  langid - character set/collation to use
  sorted - whether this column will be used to order by
  
'''langid''' is mapped to real database values by the "dblanguages" configuration option. The database may not be able to order the request column type in which case, if <tt>sorted</tt> is true, the database may use a substitute column type.

<tt>$data_type</tt> is the SQL type. The types are constants defined by this module, to import them use:

  use EPrints::Database qw( :sql_types );
  
Supported types (n = requires <tt>$length</tt> argument):

Character data: <tt>SQL_VARCHAR(n)</tt>, <tt>SQL_LONGVARCHAR</tt>, <tt>SQL_CLOB</tt>.

Binary data: <tt>SQL_VARBINARY(n)</tt>, <tt>SQL_LONGVARBINARY</tt>.

Integer data: <tt>SQL_TINYINT</tt>, <tt>SQL_SMALLINT</tt>, <tt>SQL_INTEGER</tt>, <tt>SQL_BIGINT</tt>.

Floating-point data: <tt>SQL_REAL</tt>, <tt>SQL_DOUBLE</tt>.

Time data: <tt>SQL_DATE</tt>, <tt>SQL_TIME</tt>.

The actual column types used will be database-specific.

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<!-- Pod2Wiki=head_basic_sql_operations -->
===Basic SQL Operations===
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<!-- Pod2Wiki=item_do -->
====do====

 $success = $db-&gt;do( $sql )
Execute the given <tt>$sql</tt>.

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<!-- Pod2Wiki=item_prepare -->
====prepare====

 $sth = $db-&gt;prepare( $sql )
Prepare the given <tt>$sql</tt> and return a handle on it.

Use the <tt>execute</tt> method on the returned {{API:PodLink|file=DBI|package_name=DBI|section=|text=DBI}} handle to execute the SQL:

  my $sth = $db-&gt;prepare_select( "SELECT 'Hello, World'" );
  $sth-&gt;execute;
  
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<!-- Pod2Wiki=item_prepare_select -->
====prepare_select====

 $sth = $db-&gt;prepare_select( $sql, [ %options ] )
Prepare a <tt>SELECT</tt> statement <tt>$sql</tt> and return a handle to it. After  preparing a statement use <tt>execute()</tt> to execute it.

Returns a {{API:PodLink|file=DBI|package_name=DBI|section=|text=DBI}} statement handle. 

The <tt>LIMIT</tt> SQL keyword is not universally supported, to specify this  use the <tt>limit</tt> option.

Options:

  limit - limit the number of rows returned
  offset - return '''limit''' number of rows after offset
  
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<!-- Pod2Wiki=item_execute -->
====execute====

 $success = $db-&gt;execute( $sth, $sql )
Execute the SQL prepared earlier in the <tt>$sth</tt>. <tt>$sql</tt> is only  required for debugging purposes.

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<!-- Pod2Wiki=item_update -->
====update====

 $success = $db-&gt;update( $dataset, $data, $changed )
Updates a <tt>EPrints::DataObj</tt> from <tt>$dataset</tt> with the given <tt>$data</tt>.  The primary key field (e.g. <tt>eprintid</tt>) value must be included.

Updates the <tt>ordervalues</tt> if the <tt>$dataset</tt> is  {{API:PodLink|file=EPrints/DataSet#ordered|package_name=EPrints::DataSet#ordered|section=|text=ordered}}.

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<!-- Pod2Wiki=item__update -->
====_update====

 $rows = $db-&gt;_update( $tablename, $keycols, $keyvals, $columns, @values )
Updates <tt>$columns</tt> in <tt>$tablename</tt> with <tt>@values</tt> where <tt>$keycols</tt>  equals <tt>$keyvals</tt> and returns the number of rows affected.

N.B. If no rows are affected, the result is still <tt>true</tt>,  see {{API:PodLink|file=DBI|package_name=DBI|section=|text=DBI}}'s <tt>execute()</tt> method.

This is an internal method.

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<!-- Pod2Wiki=item_insert -->
====insert====

 $success = $db-&gt;insert( $table, $columns, @values )
Inserts <tt>@values</tt> into the table <tt>$table</tt>. If <tt>$columns</tt> is defined  it will be used as a list of columns to insert into. <tt>@values</tt> is a  list of arrays containing values to insert. These will be quoted before  insertion.

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<!-- Pod2Wiki=item_insert_quoted -->
====insert_quoted====

 $success = $db-&gt;insert_quoted( $table, $columns, @qvalues )
Inserts values into the table <tt>$table</tt>. If <tt>$columns</tt> is defined it  will be used as a list of columns to insert into. <tt>@qvalues</tt> is a  list of arrays containing values to insert. These will NOT be quoted  before insertion - care must be exercised!

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<!-- Pod2Wiki=item_delete_from -->
====delete_from====

 $success = $db-&gt;delete_from( $table, $columns, @values )
Perform a SQL <tt>DELETE FROM</tt> <tt>$table</tt> using <tt>$columns</tt> to build a  where clause. <tt>@values</tt> is a list of array references of values in  the same order as <tt>$columns</tt>.

If you want to clear a table completely use <tt>clear_table()</tt>.

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<!-- Pod2Wiki=item_count_table -->
====count_table====

 $n = $db-&gt;count_table( $tablename )
Return the number of rows in the specified SQL table with  <tt>$tablename</tt>.

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<!-- Pod2Wiki=item_clear_table -->
====clear_table====

 $db-&gt;clear_table( $tablename )
Clears all records from the given table with <tt>$tablename</tt>. Use with  caution!

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<!-- Pod2Wiki=head_quoting -->
===Quoting===
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<!-- Pod2Wiki=item_prep_int -->
====prep_int====

 $mungedvalue = EPrints::Database::prep_int( $value )
Escape numerical <tt>$value</tt> for an SQL statement. <tt>undef</tt> becomes  <tt>NULL</tt>. Anything else becomes a number (zero if needed).

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<!-- Pod2Wiki=item_prep_value -->
====prep_value====

 $mungedvalue = EPrints::Database::prep_value( $value )
Escape <tt>$value</tt> for an SQL statement. Modify value such that <tt>"</tt>  becomes <tt>\"</tt> and <tt>\</tt> becomes <tt>\\</tt> and <tt>'</tt> becomes <tt>\'</tt>.

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<!-- Pod2Wiki=item_prep_like_value -->
====prep_like_value====

 $mungedvalue = EPrints::Database::prep_like_value( $value )
Escape <tt>$value</tt> for an SQL <tt>LIKE</tt> clause. In addition to <tt>'</tt> <tt>"</tt>  and <tt>\</tt> also escapes <tt>%</tt> and <tt>_</tt>.

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<!-- Pod2Wiki=item_quote_value -->
====quote_value====

 $str = $db-&gt;quote_value( $value )
Return a quoted version of <tt>$value</tt>. To quote a <tt>LIKE</tt> value  you should use:

 $db-&gt;quote_value( EPrints::Database::prep_like_value( $foo ) . '%' );
  
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<!-- Pod2Wiki=item_quote_int -->
====quote_int====

 $str = $db-&gt;quote_int( $value )
Return a quoted integer for <tt>$value</tt>.

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<!-- Pod2Wiki=item_quote_binary -->
====quote_binary====

 $str = $db-&gt;quote_binary( $bytes )
Some databases (Oracle/PostgreSQL) require transforms of binary data  to work correctly.

This method should be called on data <tt>$bytes</tt> containing null bytes  or back-slashes before being passed on [[API:EPrints/Database#quote_value|quote_value]].

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<!-- Pod2Wiki=item_quote_ordervalue -->
====quote_ordervalue====

 $str = $db-&gt;quote_ordervalue( $field, $value )
Some databases (Oracle) can't order by <tt>CLOB</tt>s so need special  treatment when creating the ordervalues tables. This method allows any  fixing-up required for string data <tt>$value</tt> for <tt>$field</tt> before it's  inserted.

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<!-- Pod2Wiki=item_quote_identifier -->
====quote_identifier====

 $str = $db-&gt;quote_identifier( @parts )
Quote a database identifier (e.g. table names). Multiple <tt>@parts</tt>  will be joined by dots (<tt>.</tt>).

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<!-- Pod2Wiki=item_prepare_regexp -->
====prepare_regexp====

 $sql = $db-&gt;prepare_regexp( $col, $value )
The syntax used for regular expressions varies across databases. This  method takes two quoted string and returns a SQL expression that will  apply the quoted regexp <tt>$value</tt> to the quoted column <tt>$col</tt>.

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<!-- Pod2Wiki=item_sql_as -->
====sql_as====

 $sql = $db-&gt;sql_AS()
Returns the syntactic glue to use when aliasing. SQL 92 databases will  happily use <tt>AS</tt> but some databases (Oracle) will not accept it.

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<!-- Pod2Wiki=item_sql_like -->
====sql_like====

 $sql = $db-&gt;sql_LIKE()
Returns the syntactic glue to use when making a case-insensitive  <tt>LIKE</tt>. PostgreSQL requires <tt>ILIKE</tt> while everything else uses  <tt>LIKE</tt> and the column collation.

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<!-- Pod2Wiki=head_counters -->
===Counters===
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<!-- Pod2Wiki=item_counter_current -->
====counter_current====

 $n = $db-&gt;counter_current( $counter )
Return the value of the previous counter_next on <tt>$counter</tt>.

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<!-- Pod2Wiki=item_counter_next -->
====counter_next====

 $n = $db-&gt;counter_next( $counter )
Return the next unused value for the named <tt>$counter</tt>. Returns  <tt>undef</tt> if the <tt>$counter</tt> doesn't exist.

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<!-- Pod2Wiki=item_counter_minimum -->
====counter_minimum====

 $db-&gt;counter_minimum( $counter, $value )
Ensure that the <tt>$counter</tt> is set no lower than <tt>$value</tt>. This is  used when importing eprints which may not be in scrict sequence.

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<!-- Pod2Wiki=item_counter_reset -->
====counter_reset====

 $db-&gt;counter_reset( $counter )
Reset the <tt>$counter</tt>. Use with caution.

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<!-- Pod2Wiki=item_next_doc_pos -->
====next_doc_pos====

 $n = $db-&gt;next_doc_pos( $eprintid )
Return the next unused document position for the given <tt>$eprintid</tt>.

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<!-- Pod2Wiki=head_dataset_data -->
===Dataset Data===
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<!-- Pod2Wiki=item_exists -->
====exists====

 $boolean = $db-&gt;exists( $dataset, $id )
Return <tt>true</tt> if there exists an [[API:EPrints/DataObj|EPrints::DataObj]] from the  <tt>$dataset</tt> with its primary key set to <tt>$id</tt>. Otherwise, return  <tt>false</tt>.

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<!-- Pod2Wiki=item_add_record -->
====add_record====

 $success = $db-&gt;add_record( $dataset, $data )
Add the given <tt>$data</tt> as a new record in the given <tt>$dataset</tt>.  <tt>$data</tt> is a reference to a hash containing values structured for a  record in the that <tt>$dataset</tt>.

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<!-- Pod2Wiki=item_remove -->
====remove====

 $success = $db-&gt;remove( $dataset, $id )
Attempts to remove the [[API:EPrints/DataObj|EPrints::DataObj]] with the primary key <tt>$id</tt>  from the specified <tt>$dataset</tt>.

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<!-- Pod2Wiki=head_searching_caching_and_object_retrieval -->
===Searching, caching and object retrieval===
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<!-- Pod2Wiki=item_cache_exp -->
====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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<!-- Pod2Wiki=item_cache -->
====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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<!-- Pod2Wiki=item_cache_table -->
====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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<!-- Pod2Wiki=item_cache_userid -->
====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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<!-- Pod2Wiki=item_get_cachemap -->
====get_cachemap====

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

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<!-- Pod2Wiki=item_search -->
====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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<!-- Pod2Wiki=item_drop_cache -->
====drop_cache====

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

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<!-- Pod2Wiki=item_from_cache -->
====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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<!-- Pod2Wiki=item_drop_orphan_cache_tables -->
====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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<!-- Pod2Wiki=item_get_cache_ids -->
====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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<!-- Pod2Wiki=item_get_values -->
====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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<!-- Pod2Wiki=item_sort_values -->
====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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<!-- Pod2Wiki=head_password_validation_and_secret_fields -->
===Password Validation and Secret Fields===
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<!-- Pod2Wiki=item_valid_login -->
====valid_login====

 $db-&gt;valid_login( $username, $password )
Returns whether the clear-text <tt>$password</tt> matches the stored crypted  password for the <tt>$username</tt>.

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<!-- Pod2Wiki=item_secret_matches -->
====secret_matches====

 $db-&gt;secret_matches( $dataobj, $fieldname, $token [, $callback ] )
Returns whether the clear-text <tt>$token</tt> matches the stored crypted  field with <tt>$fieldname</tt> for the <tt>$dataobj</tt> according to the  <tt>$callback</tt> function.

If not set, <tt>$callback</tt> defaults to [[API:EPrints/Utils#crypt_equals|EPrints::Utils#crypt_equals]].

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<!-- Pod2Wiki=item_is_secret_set -->
====is_secret_set====

 $boolean = $db-&gt;is_secret_set( $dataobj, $fieldname )
Returns a boolean for whether the secret <tt>$fieldname</tt> for <tt>$dataobj</tt>  has a value set.

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<!-- Pod2Wiki=head_database_schema_manipulation -->
===Database Schema Manipulation===
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<!-- Pod2Wiki=item_has_sequence -->
====has_sequence====

 $boolean = $db-&gt;has_sequence( $name )
Returns <tt>true</tt> if a sequence of the given <tt>$name</tt> exists in the  database. Otherwise, returns <tt>false</tt>.

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<!-- Pod2Wiki=item_create_sequence -->
====create_sequence====

 $success = $db-&gt;create_sequence( $name )
Creates a new sequence object with <tt>$name</tt> and initialises to zero.

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<!-- Pod2Wiki=item_drop_sequence -->
====drop_sequence====

 $success = $db-&gt;drop_sequence( $name )
Deletes a sequence object with <tt>$name</tt>.

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<!-- Pod2Wiki=item_has_column -->
====has_column====

 $boolean = $db-&gt;has_column( $table, $column )
Return <tt>true</tt> if the named <tt>$table</tt> has the named <tt>$column</tt> in the  database.

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<!-- Pod2Wiki=item_drop_column -->
====drop_column====

 $success = $db-&gt;drop_column( $table, $column )
Drops the named <tt>$column</tt> from the named <tt>$table</tt>.

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<!-- Pod2Wiki=item_get_primary_key -->
====get_primary_key====

 @columns = $db-&gt;get_primary_key( $tablename )
Returns a list of column names that comprise the primary key for  the <tt>$tablename</tt>.

Returns an empty list if no primary key exists.

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<!-- Pod2Wiki=item_index_name -->
====index_name====

 $name = $db-&gt;index_name( $table, @cols )
Returns the name of the first index that starts with named columns  <tt>@cols</tt> in the named <tt>$table</tt>.

Returns <tt>undef</tt> if no index exists.

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<!-- Pod2Wiki=item_get_index_ids -->
====get_index_ids====

 $ids = $db-&gt;get_index_ids( $table, $condition )
Return a reference to an array of the distinct primary keys from the named SQL <tt>$table</tt> which match the specified <tt>$condition</tt>.

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<!-- Pod2Wiki=item_create_index -->
====create_index====

 $success = $db-&gt;create_index( $table, @columns )
Creates an index over <tt>@columns</tt> for named <tt>$table</tt>. Returns <tt>true</tt>  on success, <tt>false</tt> otherwise.

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<!-- Pod2Wiki=item_create_unique_index -->
====create_unique_index====

 $success = $db-&gt;create_unique_index( $tablename, @columns )
Creates a unique index over <tt>@columns</tt> for named <tt>$table</tt>. Returns  <tt>true</tt> on success, <tt>false</tt> otherwise.

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<!-- Pod2Wiki=item_create_foreign_key -->
====create_foreign_key====

 $ok = $db-&gt;create_foreign_key( $main_table, $table, $key_field )
Create a foreign key relationship between named <tt>$main_table</tt> and  named <tt>$table</tt> using <tt>$key_field</tt>.

This will cause records in <tt>$table</tt> to be deleted if the equivalent  record is deleted from <tt>$main_table</tt>.

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<!-- Pod2Wiki=item_get_tables -->
====get_tables====

 @tables = $db-&gt;get_tables( [ $dbname ] )
Returns a list of all the tables in the database.  

<tt>$dbname</tt> specifies a particular database name of current connection has access to more than one database.

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<!-- Pod2Wiki=item_has_table -->
====has_table====

 $boolean = $db-&gt;has_table( $tablename )
Returns boolean dependent on whether a table of the <tt>$tablename</tt>  exists in the database.

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<!-- Pod2Wiki=item_create_table -->
====create_table====

 $success = $db-&gt;create_table( $tablename, $setkey, @fields );
Creates a new table with <tt>$tablename</tt> based on <tt>@fields</tt>.

The first <tt>$setkey</tt> number of fields are used for its primary key.

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<!-- Pod2Wiki=item_drop_table -->
====drop_table====

 $db-&gt;drop_table( @tables )
Delete the named <tt>@tables</tt>. Use with caution!

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<!-- Pod2Wiki=item_rename_table -->
====rename_table====

 $db-&gt;rename_table( $table_from, $table_to )
Renames the table named <tt>$table_from</tt> to <tt>$table_to</tt>.

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<!-- Pod2Wiki=item_swap_table -->
====swap_table====

 $db-&gt;swap_table( $table_a, $table_b )
Renames table named <tt>$table_a</tt> to <tt>$table_b</tt> and vice-versa. 

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<!-- Pod2Wiki=head_eprints_schema_manipulation -->
===EPrints Schema Manipulation===
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<!-- Pod2Wiki=item_create_archive_tables -->
====create_archive_tables====

 $success = $db-&gt;create_archive_tables()
Create all the SQL tables for all datasets.

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<!-- Pod2Wiki=item_drop_archive_tables -->
====drop_archive_tables====

 $db-&gt;drop_archive_tables()
Destroy all tables used by EPrints in the database.

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<!-- Pod2Wiki=item_create_version_table -->
====create_version_table====

 $db-&gt;create_version_table
Make the version table (and set the only value to be the current version of EPrints).

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<!-- Pod2Wiki=item_drop_version_table -->
====drop_version_table====

 $db-&gt;drop_version_table
Drop the version table.

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<!-- Pod2Wiki=item_has_dataset -->
====has_dataset====

 $db-&gt;has_dataset( $dataset )
Returns <tt>true</tt> if <tt>$dataset</tt> exists in the database and has all  expected tables including ordervalues and index tables.

This does not check that all fields are configured - see &lt;/has_field&gt;.

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<!-- Pod2Wiki=item_has_dataset_index_tables -->
====has_dataset_index_tables====

 $db-&gt;has_dataset_index_tables( $dataset )
Returns <tt>true</tt> if index tables for <tt>$dataset</tt> exists of if this is  not indexable.

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<!-- Pod2Wiki=item_create_dataset_tables -->
====create_dataset_tables====

 $success = $db-&gt;create_dataset_tables( $dataset )
Creates all the SQL tables for the specified <tt>$dataset</tt>.

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<!-- Pod2Wiki=item_drop_dataset_tables -->
====drop_dataset_tables====

 $db-&gt;drop_dataset_tables( $dataset )
Drops all the SQL tables for the specified <tt>$dataset</tt>.

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<!-- Pod2Wiki=item_create_dataset_index_tables -->
====create_dataset_index_tables====

 $success = $db-&gt;create_dataset_index_tables( $dataset )
Creates all the index tables for the specified <tt>$dataset</tt>.

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<!-- Pod2Wiki=item_create_dataset_ordervalues_tables -->
====create_dataset_ordervalues_tables====

 $success = $db-&gt;create_dataset_ordervalues_tables( $dataset )
Creates all the ordervalues tables for the specified <tt>$dataset</tt>.

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<!-- Pod2Wiki=item_has_field -->
====has_field====

 $db-&gt;has_field( $dataset, $field )
Returns <tt>true</tt> if <tt>$field</tt> is in the database for <tt>$dataset</tt>.

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<!-- Pod2Wiki=item_add_field -->
====add_field====

 $db-&gt;add_field( $dataset, $field, [ $force ] )
Add <tt>$field</tt> to <tt>$dataset</tt>'s tables.

If <tt>$force</tt> is <tt>true</tt> modify/replace an existing column. Use with  care!

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<!-- Pod2Wiki=item_remove_field -->
====remove_field====

 $db-&gt;remove_field( $dataset, $field )
Remove <tt>$field</tt> from <tt>$dataset</tt>'s tables.

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<!-- Pod2Wiki=item_rename_field -->
====rename_field====

 $ok = $db-&gt;rename_field( $dataset, $field, $old_name )
Rename the <tt>$field</tt> in the <tt>$dataset</tt> from its <tt>$old_name</tt>.

Returns <tt>true</tt> if the <tt>$field</tt> is successfully renamed.

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<!-- Pod2Wiki=item_create_counters -->
====create_counters====

 $success = $db-&gt;create_counters
Create the counters used to store the highest current ID of eprints, users, etc.

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====has_counter====

 $success = $db-&gt;has_counter( $counter )
Returns <tt>true</tt> if <tt>$counter</tt> exists.

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<!-- Pod2Wiki=item_create_counter -->
====create_counter====

 $success = $db-&gt;create_counter( $name )
Create and initialise to zero a new counter with <tt>$name</tt>.

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<!-- Pod2Wiki=item_remove_counters -->
====remove_counters====

 $success = $db-&gt;remove_counters
Destroy all counters.

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<!-- Pod2Wiki=item_drop_counter -->
====drop_counter====

 $success = $db-&gt;drop_counter( $name )
Destroy the counter named <tt>$name</tt>.

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<!-- Pod2Wiki=head_user_messages -->
===User Messages===
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<!-- Pod2Wiki=item_save_user_message -->
====save_user_message====

 $message = $db-&gt;save_user_message( $userid, $m_type, $dom_m_data )
Save user message provided in XML DOM object <tt>$dom_m_data</tt> as a  sanitized string in a [[API:EPrints/DataObj/Message|EPrints::DataObj::Message]] using <tt>$m_type</tt> to  define the message type and <tt>$userid</tt> for the ID of the user whose message it is.

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<!-- Pod2Wiki=item_get_user_messages -->
====get_user_messages====

 @messages = $db-&gt;get_user_messages( $userid, %opts )
Get the messages for a user with ID <tt>$userid</tt> and clear messages if <tt>$opt{clear}</tt> is set.

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<!-- Pod2Wiki=item_clear_user_messages -->
====clear_user_messages====

 $db-&gt;clear_user_messages( $userid )
Clear all messages for user with ID <tt>$userid</tt>.

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<!-- Pod2Wiki=head_see_also -->