/lib/dmllib.php

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<?php // $Id: dmllib.php,v 1.116.2.38 2011/12/01 12:25:16 moodlerobot Exp $



///////////////////////////////////////////////////////////////////////////

//                                                                       //

// NOTICE OF COPYRIGHT                                                   //

//                                                                       //

// Moodle - Modular Object-Oriented Dynamic Learning Environment         //

//          http://moodle.com                                            //

//                                                                       //

// Copyright (C) 1999 onwards Martin Dougiamas     http://dougiamas.com  //

//                                                                       //

// This program is free software; you can redistribute it and/or modify  //

// it under the terms of the GNU General Public License as published by  //

// the Free Software Foundation; either version 2 of the License, or     //

// (at your option) any later version.                                   //

//                                                                       //

// This program is distributed in the hope that it will be useful,       //

// but WITHOUT ANY WARRANTY; without even the implied warranty of        //

// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         //

// GNU General Public License for more details:                          //

//                                                                       //

//          http://www.gnu.org/copyleft/gpl.html                         //

//                                                                       //

///////////////////////////////////////////////////////////////////////////



/// This library contains all the Data Manipulation Language (DML) functions

/// used to interact with the DB. All the dunctions in this library must be

/// generic and work against the major number of RDBMS possible. This is the

/// list of currently supported and tested DBs: mysql, postresql, mssql, oracle



/// This library is automatically included by Moodle core so you never need to

/// include it yourself.



/// For more info about the functions available in this library, please visit:

///     http://docs.moodle.org/19/en/DML_functions

/// (feel free to modify, improve and document such page, thanks!)



/// GLOBAL CONSTANTS /////////////////////////////////////////////////////////



$empty_rs_cache = array();   // Keeps copies of the recordsets used in one invocation

$metadata_cache = array();   // Kereeps copies of the MetaColumns() for each table used in one invocations



$rcache = new StdClass;      // Cache simple get_record results

$rcache->data   = array();

$rcache->hits   = 0;

$rcache->misses = 0;



/// FUNCTIONS FOR DATABASE HANDLING  ////////////////////////////////



/**

 * Execute a given sql command string

 *

 * Completely general function - it just runs some SQL and reports success.

 *

 * @uses $db

 * @param string $command The sql string you wish to be executed.

 * @param bool $feedback Set this argument to true if the results generated should be printed. Default is true.

 * @return bool success

 */

function execute_sql($command, $feedback=true) {

/// Completely general function - it just runs some SQL and reports success.



    global $db, $CFG;



    $olddebug = $db->debug;



    if (!$feedback) {

        $db->debug = false;

    }



    if ($CFG->version >= 2006101007) { //Look for trailing ; from Moodle 1.7.0

        $command = trim($command);

    /// If the trailing ; is there, fix and warn!

        if (substr($command, strlen($command)-1, 1) == ';') {

        /// One noticeable exception, Oracle PL/SQL blocks require ending in ";"

            if ($CFG->dbfamily == 'oracle' && substr($command, -4) == 'END;') {

                /// Nothing to fix/warn. The command is one PL/SQL block, so it's ok.

            } else {

                $command = trim($command, ';');

                debugging('Warning. Avoid to end your SQL commands with a trailing ";".', DEBUG_DEVELOPER);

            }

        }

    }



    $empty_rs_cache = array();  // Clear out the cache, just in case changes were made to table structures



    if (defined('MDL_PERFDB')) { global $PERF ; $PERF->dbqueries++; };



    $rs = $db->Execute($command);



    $db->debug = $olddebug;



    if ($rs) {

        if ($feedback) {

            notify(get_string('success'), 'notifysuccess');

        }

        return true;

    } else {

        if ($feedback) {

            notify('<strong>' . get_string('error') . '</strong>');

        }

        // these two may go to difference places

        debugging($db->ErrorMsg() .'<br /><br />'. s($command));

        if (!empty($CFG->dblogerror)) {

            $debug=array_shift(debug_backtrace());

            error_log("SQL ".$db->ErrorMsg()." in {$debug['file']} on line {$debug['line']}. STATEMENT:  $command");

        }

        return false;

    }

}



/**

* on DBs that support it, switch to transaction mode and begin a transaction

* you'll need to ensure you call commit_sql() or your changes *will* be lost.

*

* Now using ADOdb standard transactions. Some day, we should switch to

* Smart Transactions (http://phplens.com/adodb/tutorial.smart.transactions.html)

* as they autodetect errors and are nestable and easier to write

*

* this is _very_ useful for massive updates

*/

function begin_sql() {



    global $db;



    $db->BeginTrans();



    return true;

}



/**

* on DBs that support it, commit the transaction

*

* Now using ADOdb standard transactions. Some day, we should switch to

* Smart Transactions (http://phplens.com/adodb/tutorial.smart.transactions.html)

* as they autodetect errors and are nestable and easier to write

*/

function commit_sql() {



    global $db;



    $db->CommitTrans();



    return true;

}



/**

* on DBs that support it, rollback the transaction

*

* Now using ADOdb standard transactions. Some day, we should switch to

* Smart Transactions (http://phplens.com/adodb/tutorial.smart.transactions.html)

* as they autodetect errors and are nestable and easier to write

*/

function rollback_sql() {



    global $db;



    $db->RollbackTrans();



    return true;

}



/**

 * returns db specific uppercase function

 * @deprecated Moodle 1.7 because all the RDBMS use upper()

 */

function db_uppercase() {

    return "upper";

}



/**

 * returns db specific lowercase function

 * @deprecated Moodle 1.7 because all the RDBMS use lower()

 */

function db_lowercase() {

    return "lower";

}





/**

 * Run an arbitrary sequence of semicolon-delimited SQL commands

 *

 * Assumes that the input text (file or string) consists of

 * a number of SQL statements ENDING WITH SEMICOLONS.  The

 * semicolons MUST be the last character in a line.

 * Lines that are blank or that start with "#" or "--" (postgres) are ignored.

 * Only tested with mysql dump files (mysqldump -p -d moodle)

 *

 * @uses $CFG

 *

 * @deprecated Moodle 1.7 use the new XMLDB stuff in lib/ddllib.php

 *

 * @param string $sqlfile The path where a file with sql commands can be found on the server.

 * @param string $sqlstring If no path is supplied then a string with semicolon delimited sql

 * commands can be supplied in this argument.

 * @return bool Returns true if databse was modified successfully.

 */

function modify_database($sqlfile='', $sqlstring='') {



    global $CFG;



    if ($CFG->version > 2006101007) {

        debugging('Function modify_database() is deprecated. Replace it with the new XMLDB stuff.', DEBUG_DEVELOPER);

    }



    $success = true;  // Let's be optimistic



    if (!empty($sqlfile)) {

        if (!is_readable($sqlfile)) {

            $success = false;

            echo '<p>Tried to modify database, but "'. $sqlfile .'" doesn\'t exist!</p>';

            return $success;

        } else {

            $lines = file($sqlfile);

        }

    } else {

        $sqlstring = trim($sqlstring);

        if ($sqlstring{strlen($sqlstring)-1} != ";") {

            $sqlstring .= ";"; // add it in if it's not there.

        }

        $lines[] = $sqlstring;

    }



    $command = '';



    foreach ($lines as $line) {

        $line = rtrim($line);

        $length = strlen($line);



        if ($length and $line[0] <> '#' and $line[0].$line[1] <> '--') {

            if (substr($line, $length-1, 1) == ';') {

                $line = substr($line, 0, $length-1);   // strip ;

                $command .= $line;

                $command = str_replace('prefix_', $CFG->prefix, $command); // Table prefixes

                if (! execute_sql($command)) {

                    $success = false;

                }

                $command = '';

            } else {

                $command .= $line;

            }

        }

    }



    return $success;



}



/// GENERIC FUNCTIONS TO CHECK AND COUNT RECORDS ////////////////////////////////////////



/**

 * Test whether a record exists in a table where all the given fields match the given values.

 *

 * The record to test is specified by giving up to three fields that must

 * equal the corresponding values.

 *

 * @uses $CFG

 * @param string $table The table to check.

 * @param string $field1 the first field to check (optional).

 * @param string $value1 the value field1 must have (requred if field1 is given, else optional).

 * @param string $field2 the second field to check (optional).

 * @param string $value2 the value field2 must have (requred if field2 is given, else optional).

 * @param string $field3 the third field to check (optional).

 * @param string $value3 the value field3 must have (requred if field3 is given, else optional).

 * @return bool true if a matching record exists, else false.

 */

function record_exists($table, $field1='', $value1='', $field2='', $value2='', $field3='', $value3='') {



    global $CFG;



    $select = where_clause($field1, $value1, $field2, $value2, $field3, $value3);



    return record_exists_sql('SELECT * FROM '. $CFG->prefix . $table .' '. $select);

}



/**

 * Test whether any records exists in a table which match a particular WHERE clause.

 *

 * @uses $CFG

 * @param string $table The database table to be checked against.

 * @param string $select A fragment of SQL to be used in a WHERE clause in the SQL call.

 * @return bool true if a matching record exists, else false.

 */

function record_exists_select($table, $select='') {



    global $CFG;



    if ($select) {

        $select = 'WHERE '.$select;

    }



    return record_exists_sql('SELECT * FROM '. $CFG->prefix . $table . ' ' . $select);

}



/**

 * Test whether a SQL SELECT statement returns any records.

 *

 * This function returns true if the SQL statement executes

 * without any errors and returns at least one record.

 *

 * @param string $sql The SQL statement to execute.

 * @return bool true if the SQL executes without errors and returns at least one record.

 */

function record_exists_sql($sql) {



    $limitfrom = 0; /// Number of records to skip

    $limitnum  = 1; /// Number of records to retrieve



    if (!$rs = get_recordset_sql($sql, $limitfrom, $limitnum)) {

        return false;

    }



    if (rs_EOF($rs)) {

        $result = false;

    } else {

        $result = true;

    }



    rs_close($rs);

    return $result;

}



/**

 * Count the records in a table where all the given fields match the given values.

 *

 * @uses $CFG

 * @param string $table The table to query.

 * @param string $field1 the first field to check (optional).

 * @param string $value1 the value field1 must have (requred if field1 is given, else optional).

 * @param string $field2 the second field to check (optional).

 * @param string $value2 the value field2 must have (requred if field2 is given, else optional).

 * @param string $field3 the third field to check (optional).

 * @param string $value3 the value field3 must have (requred if field3 is given, else optional).

 * @return int The count of records returned from the specified criteria.

 */

function count_records($table, $field1='', $value1='', $field2='', $value2='', $field3='', $value3='') {



    global $CFG;



    $select = where_clause($field1, $value1, $field2, $value2, $field3, $value3);



    return count_records_sql('SELECT COUNT(*) FROM '. $CFG->prefix . $table .' '. $select);

}



/**

 * Count the records in a table which match a particular WHERE clause.

 *

 * @uses $CFG

 * @param string $table The database table to be checked against.

 * @param string $select A fragment of SQL to be used in a WHERE clause in the SQL call.

 * @param string $countitem The count string to be used in the SQL call. Default is COUNT(*).

 * @return int The count of records returned from the specified criteria.

 */

function count_records_select($table, $select='', $countitem='COUNT(*)') {



    global $CFG;



    if ($select) {

        $select = 'WHERE '.$select;

    }



    return count_records_sql('SELECT '. $countitem .' FROM '. $CFG->prefix . $table .' '. $select);

}



/**

 * Get the result of a SQL SELECT COUNT(...) query.

 *

 * Given a query that counts rows, return that count. (In fact,

 * given any query, return the first field of the first record

 * returned. However, this method should only be used for the

 * intended purpose.) If an error occurrs, 0 is returned.

 *

 * @uses $CFG

 * @uses $db

 * @param string $sql The SQL string you wish to be executed.

 * @return int the count. If an error occurrs, 0 is returned.

 */

function count_records_sql($sql) {

    $rs = get_recordset_sql($sql);



    if (is_object($rs) and is_array($rs->fields)) {

        return reset($rs->fields);

    } else {

        return 0;

    }

}



/// GENERIC FUNCTIONS TO GET, INSERT, OR UPDATE DATA  ///////////////////////////////////





/**

 * Get a single record as an object

 *

 * @uses $CFG

 * @param string $table The table to select from.

 * @param string $field1 the first field to check (optional).

 * @param string $value1 the value field1 must have (requred if field1 is given, else optional).

 * @param string $field2 the second field to check (optional).

 * @param string $value2 the value field2 must have (requred if field2 is given, else optional).

 * @param string $field3 the third field to check (optional).

 * @param string $value3 the value field3 must have (requred if field3 is given, else optional).

 * @return mixed a fieldset object containing the first mathcing record, or false if none found.

 */

function get_record($table, $field1, $value1, $field2='', $value2='', $field3='', $value3='', $fields='*') {



    global $CFG;



    // Check to see whether this record is eligible for caching (fields=*, only condition is id)

    $docache = false;

    if (!empty($CFG->rcache) && $CFG->rcache === true && $field1=='id' && !$field2 && !$field3 && $fields=='*') {

        $docache = true;

        // If it's in the cache, return it

        $cached = rcache_getforfill($table, $value1);

        if (!empty($cached)) {

            return $cached;

        }

    }



    $select = where_clause($field1, $value1, $field2, $value2, $field3, $value3);



    $record = get_record_sql('SELECT '.$fields.' FROM '. $CFG->prefix . $table .' '. $select);



    // If we're caching records, store this one

    // (supposing we got something - we don't cache failures)

    if ($docache) {

        if ($record !== false) {

            rcache_set($table, $value1, $record);

        } else {

            rcache_releaseforfill($table, $value1);

        }

    }

    return $record;

}



/**

 * Get a single record as an object using an SQL statement

 *

 * The SQL statement should normally only return one record. In debug mode

 * you will get a warning if more record is returned (unless you

 * set $expectmultiple to true). In non-debug mode, it just returns

 * the first record.

 *

 * @uses $CFG

 * @uses $db

 * @param string $sql The SQL string you wish to be executed, should normally only return one record.

 * @param bool $expectmultiple If the SQL cannot be written to conveniently return just one record,

 *      set this to true to hide the debug message.

 * @param bool $nolimit sometimes appending ' LIMIT 1' to the SQL causes an error. Set this to true

 *      to stop your SQL being modified. This argument should probably be deprecated.

 * @return Found record as object. False if not found or error

 */

function get_record_sql($sql, $expectmultiple=false, $nolimit=false) {



    global $CFG;



/// Default situation

    $limitfrom = 0; /// Number of records to skip

    $limitnum  = 1; /// Number of records to retrieve



/// Only a few uses of the 2nd and 3rd parameter have been found

/// I think that we should avoid to use them completely, one

/// record is one record, and everything else should return error.

/// So the proposal is to change all the uses, (4-5 inside Moodle

/// Core), drop them from the definition and delete the next two

/// "if" sentences. (eloy, 2006-08-19)



    if ($nolimit) {

        $limitfrom = 0;

        $limitnum  = 0;

    } else if ($expectmultiple) {

        $limitfrom = 0;

        $limitnum  = 1;

    } else if (debugging('', DEBUG_DEVELOPER)) {

        // Debugging mode - don't use a limit of 1, but do change the SQL, because sometimes that

        // causes errors, and in non-debug mode you don't see the error message and it is

        // impossible to know what's wrong.

        $limitfrom = 0;

        $limitnum  = 100;

    }



    if (!$rs = get_recordset_sql($sql, $limitfrom, $limitnum)) {

        return false;

    }



    $recordcount = $rs->RecordCount();



    if ($recordcount == 0) {          // Found no records

        return false;



    } else if ($recordcount == 1) {    // Found one record

    /// DIRTY HACK to retrieve all the ' ' (1 space) fields converted back

    /// to '' (empty string) for Oracle. It's the only way to work with

    /// all those NOT NULL DEFAULT '' fields until we definitively delete them

        if ($CFG->dbfamily == 'oracle') {

            array_walk($rs->fields, 'onespace2empty');

        }

    /// End of DIRTY HACK

        return (object)$rs->fields;



    } else {                          // Error: found more than one record

        notify('Error:  Turn off debugging to hide this error.');

        notify($sql . '(with limits ' . $limitfrom . ', ' . $limitnum . ')');

        if ($records = $rs->GetAssoc(true)) {

            notify('Found more than one record in get_record_sql !');

            print_object($records);

        } else {

            notify('Very strange error in get_record_sql !');

            print_object($rs);

        }

        print_continue("$CFG->wwwroot/$CFG->admin/config.php");

    }

}



/**

 * Gets one record from a table, as an object

 *

 * @uses $CFG

 * @param string $table The database table to be checked against.

 * @param string $select A fragment of SQL to be used in a where clause in the SQL call.

 * @param string $fields A comma separated list of fields to be returned from the chosen table.

 * @return object|false Returns an array of found records (as objects) or false if no records or error occured.

 */

function get_record_select($table, $select='', $fields='*') {



    global $CFG;



    if ($select) {

        $select = 'WHERE '. $select;

    }



    return get_record_sql('SELECT '. $fields .' FROM '. $CFG->prefix . $table .' '. $select);

}



/**

 * Get a number of records as an ADODB RecordSet.

 *

 * Selects records from the table $table.

 *

 * If specified, only records where the field $field has value $value are retured.

 *

 * If specified, the results will be sorted as specified by $sort. This

 * is added to the SQL as "ORDER BY $sort". Example values of $sort

 * mightbe "time ASC" or "time DESC".

 *

 * If $fields is specified, only those fields are returned.

 *

 * Since this method is a little less readable, use of it should be restricted to 

 * code where it's possible there might be large datasets being returned.  For known 

 * small datasets use get_records - it leads to simpler code.

 *

 * If you only want some of the records, specify $limitfrom and $limitnum.

 * The query will skip the first $limitfrom records (according to the sort

 * order) and then return the next $limitnum records. If either of $limitfrom

 * or $limitnum is specified, both must be present.

 *

 * The return value is an ADODB RecordSet object

 * @link http://phplens.com/adodb/reference.functions.adorecordset.html

 * if the query succeeds. If an error occurrs, false is returned.

 *

 * @param string $table the table to query.

 * @param string $field a field to check (optional).

 * @param string $value the value the field must have (requred if field1 is given, else optional).

 * @param string $sort an order to sort the results in (optional, a valid SQL ORDER BY parameter).

 * @param string $fields a comma separated list of fields to return (optional, by default all fields are returned).

 * @param int $limitfrom return a subset of records, starting at this point (optional, required if $limitnum is set).

 * @param int $limitnum return a subset comprising this many records (optional, required if $limitfrom is set).

 * @return mixed an ADODB RecordSet object, or false if an error occured.

 */

function get_recordset($table, $field='', $value='', $sort='', $fields='*', $limitfrom='', $limitnum='') {



    if ($field) {

        $value = sql_magic_quotes_hack($value);

        $select = "$field = '$value'";

    } else {

        $select = '';

    }



    return get_recordset_select($table, $select, $sort, $fields, $limitfrom, $limitnum);

}



/**

 * Get a number of records as an ADODB RecordSet.

 *

 * If given, $select is used as the SELECT parameter in the SQL query,

 * otherwise all records from the table are returned.

 *

 * Other arguments and the return type as for @see function get_recordset.

 *

 * @uses $CFG

 * @param string $table the table to query.

 * @param string $select A fragment of SQL to be used in a where clause in the SQL call.

 * @param string $sort an order to sort the results in (optional, a valid SQL ORDER BY parameter).

 * @param string $fields a comma separated list of fields to return (optional, by default all fields are returned).

 * @param int $limitfrom return a subset of records, starting at this point (optional, required if $limitnum is set).

 * @param int $limitnum return a subset comprising this many records (optional, required if $limitfrom is set).

 * @return mixed an ADODB RecordSet object, or false if an error occured.

 */

function get_recordset_select($table, $select='', $sort='', $fields='*', $limitfrom='', $limitnum='') {



    global $CFG;



    if ($select) {

        $select = ' WHERE '. $select;

    }



    if ($sort) {

        $sort = ' ORDER BY '. $sort;

    }



    return get_recordset_sql('SELECT '. $fields .' FROM '. $CFG->prefix . $table . $select . $sort, $limitfrom, $limitnum);

}



/**

 * Get a number of records as an ADODB RecordSet.

 *

 * Only records where $field takes one of the values $values are returned.

 * $values should be a comma-separated list of values, for example "4,5,6,10"

 * or "'foo','bar','baz'".

 *

 * Other arguments and the return type as for @see function get_recordset.

 *

 * @param string $table the table to query.

 * @param string $field a field to check (optional).

 * @param string $values comma separated list of values the field must have (requred if field is given, else optional).

 * @param string $sort an order to sort the results in (optional, a valid SQL ORDER BY parameter).

 * @param string $fields a comma separated list of fields to return (optional, by default all fields are returned).

 * @param int $limitfrom return a subset of records, starting at this point (optional, required if $limitnum is set).

 * @param int $limitnum return a subset comprising this many records (optional, required if $limitfrom is set).

 * @return mixed an ADODB RecordSet object, or false if an error occured.

 */

function get_recordset_list($table, $field='', $values='', $sort='', $fields='*', $limitfrom='', $limitnum='') {



    if ($field) {

        $select = "$field IN ($values)";

    } else {

        $select = '';

    }



    return get_recordset_select($table, $select, $sort, $fields, $limitfrom, $limitnum);

}



/**

 * Get a number of records as an ADODB RecordSet.  $sql must be a complete SQL query.

 * Since this method is a little less readable, use of it should be restricted to 

 * code where it's possible there might be large datasets being returned.  For known 

 * small datasets use get_records_sql - it leads to simpler code.

 *

 * The return type is as for @see function get_recordset.

 *

 * @uses $CFG

 * @uses $db

 * @param string $sql the SQL select query to execute.

 * @param int $limitfrom return a subset of records, starting at this point (optional, required if $limitnum is set).

 * @param int $limitnum return a subset comprising this many records (optional, required if $limitfrom is set).

 * @return mixed an ADODB RecordSet object, or false if an error occured.

 */

function get_recordset_sql($sql, $limitfrom=null, $limitnum=null) {

    global $CFG, $db;



    if (empty($db)) {

        return false;

    }



/// Temporary hack as part of phasing out all access to obsolete user tables  XXX

    if (!empty($CFG->rolesactive)) {

        if (strpos($sql, ' '.$CFG->prefix.'user_students ') ||

            strpos($sql, ' '.$CFG->prefix.'user_teachers ') ||

            strpos($sql, ' '.$CFG->prefix.'user_coursecreators ') ||

            strpos($sql, ' '.$CFG->prefix.'user_admins ')) {

            if (debugging()) { var_dump(debug_backtrace()); }

            error('This SQL relies on obsolete tables!  Your code must be fixed by a developer.');

        }

    }





    if (defined('MDL_PERFDB')) { global $PERF ; $PERF->dbqueries++; };



    if ($limitfrom || $limitnum) {

        ///Special case, 0 must be -1 for ADOdb

        $limitfrom = empty($limitfrom) ? -1 : $limitfrom;

        $limitnum  = empty($limitnum) ? -1 : $limitnum;

        $rs = $db->SelectLimit($sql, $limitnum, $limitfrom);

    } else {

        $rs = $db->Execute($sql);

    }

    if (!$rs) {

        debugging($db->ErrorMsg() .'<br /><br />'. s($sql));

        if (!empty($CFG->dblogerror)) {

            $debug=array_shift(debug_backtrace());

            error_log("SQL ".$db->ErrorMsg()." in {$debug['file']} on line {$debug['line']}. STATEMENT:  $sql with limits ($limitfrom, $limitnum)");

        }

        return false;

    }



    return $rs;

}



/**

 * Utility function used by the following 4 methods. Note that for this to work, the first column

 * in the recordset must contain unique values, as it is used as the key to the associative array.

 *

 * @param object an ADODB RecordSet object.

 * @return mixed mixed an array of objects, or false if an error occured or the RecordSet was empty.

 */

function recordset_to_array($rs) {

    global $CFG;



    $debugging = debugging('', DEBUG_DEVELOPER);



    if ($rs && !rs_EOF($rs)) {

        $objects = array();

    /// First of all, we are going to get the name of the first column

    /// to introduce it back after transforming the recordset to assoc array

    /// See http://docs.moodle.org/19/en/XMLDB_Problems, fetch mode problem.

        $firstcolumn = $rs->FetchField(0);

    /// Get the whole associative array

        if ($records = $rs->GetAssoc(true)) {

            foreach ($records as $key => $record) {

            /// Really DIRTY HACK for Oracle, but it's the only way to make it work

            /// until we got all those NOT NULL DEFAULT '' out from Moodle

                if ($CFG->dbfamily == 'oracle') {

                    array_walk($record, 'onespace2empty');

                }

            /// End of DIRTY HACK

                $record[$firstcolumn->name] = $key;/// Re-add the assoc field

                if ($debugging && array_key_exists($key, $objects)) {

                    debugging("Did you remember to make the first column something unique in your call to get_records? Duplicate value '$key' found in column '".$firstcolumn->name."'.", DEBUG_DEVELOPER);

                }

                $objects[$key] = (object) $record; /// To object

            }

            return $objects;

    /// Fallback in case we only have 1 field in the recordset. MDL-5877

        } else if ($rs->_numOfFields == 1 && $records = $rs->GetRows()) {

            foreach ($records as $key => $record) {

            /// Really DIRTY HACK for Oracle, but it's the only way to make it work

            /// until we got all those NOT NULL DEFAULT '' out from Moodle

                if ($CFG->dbfamily == 'oracle') {

                    array_walk($record, 'onespace2empty');

                }

            /// End of DIRTY HACK

                if ($debugging && array_key_exists($record[$firstcolumn->name], $objects)) {

                    debugging("Did you remember to make the first column something unique in your call to get_records? Duplicate value '".$record[$firstcolumn->name]."' found in column '".$firstcolumn->name."'.", DEBUG_DEVELOPER);

                }

                $objects[$record[$firstcolumn->name]] = (object) $record; /// The key is the first column value (like Assoc)

            }

            return $objects;

        } else {

            return false;

        }

    } else {

        return false;

    }

}



/**

 * This function is used to get the current record from the recordset. It

 * doesn't advance the recordset position. You'll need to do that by

 * using the rs_next_record($recordset) function.

 * @param ADORecordSet the recordset to fetch current record from

 * @return ADOFetchObj the object containing the fetched information

 */

function rs_fetch_record(&$rs) {

    global $CFG;



    if (!$rs) {

        debugging('Incorrect $rs used!', DEBUG_DEVELOPER);

        return false;

    }



    $rec = $rs->FetchObj(); //Retrieve record as object without advance the pointer



    if ($rs->EOF) { //FetchObj requires manual checking of EOF to detect if it's the last record

        $rec = false;

    } else {

    /// DIRTY HACK to retrieve all the ' ' (1 space) fields converted back

    /// to '' (empty string) for Oracle. It's the only way to work with

    /// all those NOT NULL DEFAULT '' fields until we definetively delete them

        if ($CFG->dbfamily == 'oracle') {

            $recarr = (array)$rec; /// Cast to array

            array_walk($recarr, 'onespace2empty');

            $rec = (object)$recarr;/// Cast back to object

        }

    /// End DIRTY HACK

    }



    return $rec;

}



/**

 * This function is used to advance the pointer of the recordset

 * to its next position/record.

 * @param ADORecordSet the recordset to be moved to the next record

 * @return boolean true if the movement was successful and false if not (end of recordset)

 */

function rs_next_record(&$rs) {

    if (!$rs) {

        debugging('Incorrect $rs used!', DEBUG_DEVELOPER);

        return false;

    }



    return $rs->MoveNext(); //Move the pointer to the next record

}



/**

 * This function is used to get the current record from the recordset. It

 * does advance the recordset position.

 * This is the prefered way to iterate over recordsets with code blocks like this:

 *

 * $rs = get_recordset('SELECT .....');

 * while ($rec = rs_fetch_next_record($rs)) {

 *     /// Perform actions with the $rec record here

 * }

 * rs_close($rs); /// Close the recordset if not used anymore. Saves memory (optional but recommended).

 *

 * @param ADORecordSet the recordset to fetch current record from

 * @return mixed ADOFetchObj the object containing the fetched information or boolean false if no record (end of recordset)

 */

function rs_fetch_next_record(&$rs) {



    global $CFG;



    if (!$rs) {

        debugging('Incorrect $rs used!', DEBUG_DEVELOPER);

        return false;

    }



    $rec = false;

    $recarr = $rs->FetchRow(); //Retrieve record as object without advance the pointer. It's quicker that FetchNextObj()



    if ($recarr) {

    /// DIRTY HACK to retrieve all the ' ' (1 space) fields converted back

    /// to '' (empty string) for Oracle. It's the only way to work with

    /// all those NOT NULL DEFAULT '' fields until we definetively delete them

        if ($CFG->dbfamily == 'oracle') {

            array_walk($recarr, 'onespace2empty');

        }

    /// End DIRTY HACK

    /// Cast array to object

        $rec = (object)$recarr;

    }



    return $rec;

}



/**

 * Returns true if no more records found

 * @param ADORecordSet the recordset

 * @return bool

 */

function rs_EOF($rs) {

    if (!$rs) {

        debugging('Incorrect $rs used!', DEBUG_DEVELOPER);

        return true;

    }

    return $rs->EOF;

}



/**

 * This function closes the recordset, freeing all the memory and associated resources.

 * Note that, once closed, the recordset must not be used anymore along the request.

 * Saves memory (optional but recommended).

 * @param ADORecordSet the recordset to be closed

 * @return void

 */

function rs_close(&$rs) {

    if (!$rs) {

        debugging('Incorrect $rs used!', DEBUG_DEVELOPER);

        return;

    }



    $rs->Close();

}



/**

 * This function is used to convert all the Oracle 1-space defaults to the empty string

 * like a really DIRTY HACK to allow it to work better until all those NOT NULL DEFAULT ''

 * fields will be out from Moodle.

 * @param string the string to be converted to '' (empty string) if it's ' ' (one space)

 * @param mixed the key of the array in case we are using this function from array_walk,

 *              defaults to null for other (direct) uses

 * @return boolean always true (the converted variable is returned by reference)

 */

function onespace2empty(&$item, $key=null) {

    $item = $item == ' ' ? '' : $item;

    return true;

}

///End DIRTY HACK





/**

 * Get a number of records as an array of objects.

 *

 * If the query succeeds and returns at least one record, the

 * return value is an array of objects, one object for each

 * record found. The array key is the value from the first

 * column of the result set. The object associated with that key

 * has a member variable for each column of the results.

 *

 * @param string $table the table to query.

 * @param string $field a field to check (optional).

 * @param string $value the value the field must have (requred if field1 is given, else optional).

 * @param string $sort an order to sort the results in (optional, a valid SQL ORDER BY parameter).

 * @param string $fields a comma separated list of fields to return (optional, by default

 *   all fields are returned). The first field will be used as key for the

 *   array so must be a unique field such as 'id'.

 * @param int $limitfrom return a subset of records, starting at this point (optional, required if $limitnum is set).

 * @param int $limitnum return a subset comprising this many records (optional, required if $limitfrom is set).

 * @return mixed an array of objects, or false if no records were found or an error occured.

 */

function get_records($table, $field='', $value='', $sort='', $fields='*', $limitfrom='', $limitnum='') {

    $rs = get_recordset($table, $field, $value, $sort, $fields, $limitfrom, $limitnum);

    return recordset_to_array($rs);

}



/**

 * Get a number of records as an array of objects.

 *

 * Return value as for @see function get_records.

 *

 * @param string $table the table to query.

 * @param string $select A fragment of SQL to be used in a where clause in the SQL call.

 * @param string $sort an order to sort the results in (optional, a valid SQL ORDER BY parameter).

 * @param string $fields a comma separated list of fields to return

 *   (optional, by default all fields are returned). The first field will be used as key for the

 *   array so must be a unique field such as 'id'.

 * @param int $limitfrom return a subset of records, starting at this point (optional, required if $limitnum is set).

 * @param int $limitnum return a subset comprising this many records (optional, required if $limitfrom is set).

 * @return mixed an array of objects, or false if no records were found or an error occured.

 */

function get_records_select($table, $select='', $sort='', $fields='*', $limitfrom='', $limitnum='') {

    $rs = get_recordset_select($table, $select, $sort, $fields, $limitfrom, $limitnum);

    return recordset_to_array($rs);

}



/**

 * Get a number of records as an array of objects.

 *

 * Return value as for @see function get_records.

 *

 * @param string $table The database table to be checked against.

 * @param string $field The field to search

 * @param string $values Comma separated list of possible value

 * @param string $sort Sort order (as valid SQL sort parameter)

 * @param string $fields A comma separated list of fields to be returned from the chosen table. If specified,

 *   the first field should be a unique one such as 'id' since it will be used as a key in the associative

 *   array.

 * @return mixed an array of objects, or false if no records were found or an error occured.

 */

function get_records_list($table, $field='', $values='', $sort='', $fields='*', $limitfrom='', $limitnum='') {

    $rs = get_recordset_list($table, $field, $values, $sort, $fields, $limitfrom, $limitnum);

    return recordset_to_array($rs);

}



/**

 * Get a number of records as an array of objects.

 *

 * Return value as for @see function get_records.

 *

 * @param string $sql the SQL select query to execute. The first column of this SELECT statement

 *   must be a unique value (usually the 'id' field), as it will be used as the key of the

 *   returned array.

 * @param int $limitfrom return a subset of records, starting at this point (optional, required if $limitnum is set).

 * @param int $limitnum return a subset comprising this many records (optional, required if $limitfrom is set).

 * @return mixed an array of objects, or false if no records were found or an error occured.

 */

function get_records_sql($sql, $limitfrom='', $limitnum='') {

    $rs = get_recordset_sql($sql, $limitfrom, $limitnum);

    return recordset_to_array($rs);

}



/**

 * Utility function used by the following 3 methods.

 *

 * @param object an ADODB RecordSet object with two columns.

 * @return mixed an associative array, or false if an error occured or the RecordSet was empty.

 */

function recordset_to_menu($rs) {

    global $CFG;

    $menu = array();

    if ($rs && !rs_EOF($rs)) {

        $keys = array_keys($rs->fields);

        $key0=$keys[0];

        $key1=$keys[1];

        while (!$rs->EOF) {

            $menu[$rs->fields[$key0]] = $rs->fields[$key1];

            $rs->MoveNext();

        }

        /// Really DIRTY HACK for Oracle, but it's the only way to make it work

        /// until we got all those NOT NULL DEFAULT '' out from Moodle

        if ($CFG->dbfamily == 'oracle') {

            array_walk($menu, 'onespace2empty');

        }

        /// End of DIRTY HACK

        return $menu;

    } else {

        return false;

    }

}



/**

 * Utility function 

 * Similar to recordset_to_menu 

 *

 * field1, field2 is needed because the order from get_records_sql is not reliable

 * @param records - records from get_records_sql() or get_records()

 * @param field1 - field to be used as menu index

 * @param field2 - feild to be used as coresponding menu value

 * @return mixed an associative array, or false if an error occured or the RecordSet was empty.

 */

function records_to_menu($records, $field1, $field2) {



    $menu = array();

    foreach ($records as $record) {

        $menu[$record->$field1] = $record->$field2;

    }



    if (!empty($menu)) {

        return $menu;

    } else {

        return false; 

    }

}



/**

 * Get the first two columns from a number of records as an associative array.

 *

 * Arguments as for @see function get_recordset.

 *

 * If no errors occur, and at least one records is found, the return value

 * is an associative whose keys come from the first field of each record,

 * and whose values are the corresponding second fields. If no records are found,

 * or an error occurs, false is returned.

 *

 * @param string $table the table to query.

 * @param string $field a field to check (optional).

 * @param string $value the value the field must have (requred if field1 is given, else optional).

 * @param string $sort an order to sort the results in (optional, a valid SQL ORDER BY parameter).

 * @param string $fields a comma separated list of fields to return (optional, by default all fields are returned).

 * @param int $limitfrom return a subset of records, starting at this point (optional, required if $limitnum is set).

 * @param int $limitnum return a subset comprising this many records (optional, required if $limitfrom is set).

 * @return mixed an associative array, or false if no records were found or an error occured.

 */

function get_records_menu($table, $field='', $value='', $sort='', $fields='*', $limitfrom='', $limitnum='') {

    $rs = get_recordset($table, $field, $value, $sort, $fields, $limitfrom, $limitnum);

    return recordset_to_menu($rs);

}



/**

 * Get the first two columns from a number of records as an associative array.

 *

 * Arguments as for @see function get_recordset_select.

 * Return value as for @see function get_records_menu.

 *

 * @param string $table The database table to be checked against.

 * @param string $select A fragment of SQL to be used in a where clause in the SQL call.

 * @param string $sort Sort order (optional) - a valid SQL order parameter

 * @param string $fields A comma separated list of fields to be returned from the chosen table.

 * @param int $limitfrom return a subset of records, starting at this point (optional, required if $limitnum is set).

 * @param int $limitnum return a subset comprising this many records (optional, required if $limitfrom is set).

 * @return mixed an associative array, or false if no records were found or an error occured.

 */

function get_records_select_menu($table, $select='', $sort='', $fields='*', $limitfrom='', $limitnum='') {

    $rs = get_recordset_select($table, $select, $sort, $fields, $limitfrom, $limitnum);

    return recordset_to_menu($rs);

}



/**

 * Get the first two columns from a number of records as an associative array.

 *

 * Arguments as for @see function get_recordset_sql.

 * Return value as for @see function get_records_menu.

 *

 * @param string $sql The SQL string you wish to be executed.

 * @param int $limitfrom return a subset of records, starting at this point (optional, required if $limitnum is set).

 * @param int $limitnum return a subset comprising this many records (optional, required if $limitfrom is set).

 * @return mixed an associative array, or false if no records were found or an error occured.

 */

function get_records_sql_menu($sql, $limitfrom='', $limitnum='') {

    $rs = get_recordset_sql($sql, $limitfrom, $limitnum);

    return recordset_to_menu($rs);

}



/**

 * Get a single value from a table row where all the given fields match the given values.

 *

 * @param string $table the table to query.

 * @param string $return the field to return the value of.

 * @param string $field1 the first field to check (optional).

 * @param string $value1 the value field1 must have (requred if field1 is given, else optional).

 * @param string $field2 the second field to check (optional).

 * @param string $value2 the value field2 must have (requred if field2 is given, else optional).

 * @param string $field3 the third field to check (optional).

 * @param string $value3 the value field3 must have (requred if field3 is given, else optional).

 * @return mixed the specified value, or false if an error occured.

 */

function get_field($table, $return, $field1, $value1, $field2='', $value2='', $field3='', $value3='') {

    global $CFG;

    $select = where_clause($field1, $value1, $field2, $value2, $field3, $value3);

    return get_field_sql('SELECT ' . $return . ' FROM ' . $CFG->prefix . $table . ' ' . $select);

}



/**

 * Get a single value from a table row where a particular select clause is true.

 *

 * @uses $CFG

 * @param string $table the table to query.

 * @param string $return the field to return the value of.

 * @param string $select A fragment of SQL to be used in a where clause in the SQL call.

 * @return mixed the specified value, or false if an error occured.

 */

function get_field_select($table, $return, $select) {

    global $CFG;

    if ($select) {

        $select = 'WHERE '. $select;

    }

    return get_field_sql('SELECT ' . $return . ' FROM ' . $CFG->prefix . $table . ' ' . $select);

}



/**

 * Get a single value from a table.

 *

 * @param string $sql an SQL statement expected to return a single value.

 * @return mixed the specified value, or false if an error occured.

 */

function get_field_sql($sql) {

    global $CFG;



/// Strip potential LIMIT uses arriving here, debugging them (MDL-7173)

    $newsql = preg_replace('/ LIMIT [0-9, ]+$/is', '', $sql);

    if ($newsql != $sql) {

        debugging('Incorrect use of LIMIT clause (not cross-db) in call to get_field_sql(): ' . s($sql), DEBUG_DEVELOPER);

        $sql = $newsql;

    }



    $rs = get_recordset_sql($sql, 0, 1);



    if ($rs && $rs->RecordCount() == 1) {

        /// DIRTY HACK to retrieve all the ' ' (1 space) fields converted back

        /// to '' (empty string) for Oracle. It's the only way to work with

        /// all those NOT NULL DEFAULT '' fields until we definetively delete them

        if ($CFG->dbfamily == 'oracle') {

            $value = reset($rs->fields);

            onespace2empty($value);

            return $value;

        }

        /// End of DIRTY HACK

        return reset($rs->fields);

    } else {

        return false;

    }

}



/**

 * Get a single value from a table row where a particular select clause is true.

 *

 * @uses $CFG

 * @param string $table the table to query.

 * @param string $return the field to return the value of.

 * @param string $select A fragment of SQL to be used in a where clause in the SQL call.

 * @return mixed|false Returns the value return from the SQL statment or false if an error occured.

 */

function get_fieldset_select($table, $return, $select) {

    global $CFG;

    if ($select) {

        $select = ' WHERE '. $select;

    }

    return get_fieldset_sql('SELECT ' . $return . ' FROM ' . $CFG->prefix . $table . $select);

}



/**

 * Get an array of data from one or more fields from a database

 * use to get a column, or a series of distinct values

 *

 * @uses $CFG

 * @uses $db

 * @param string $sql The SQL string you wish to be executed.

 * @return mixed|false Returns the value return from the SQL statment or false if an error occured.

 * @todo Finish documenting this function

 */

function get_fieldset_sql($sql) {



    global $db, $CFG;



    if (defined('MDL_PERFDB')) { global $PERF ; $PERF->dbqueries++; };



    $rs = $db->Execute($sql);

    if (!$rs) {

        debugging($db->ErrorMsg() .'<br /><br />'. s($sql));

        if (!empty($CFG->dblogerror)) {

            $debug=array_shift(debug_backtrace());

            error_log("SQL ".$db->ErrorMsg()." in {$debug['file']} on line {$debug['line']}. STATEMENT:  $sql");

        }

        return false;

    }



    if ( !rs_EOF($rs) ) {

        $keys = array_keys($rs->fields);

        $key0 = $keys[0];

        $results = array();

        while (!$rs->EOF) {

            array_push($results, $rs->fields[$key0]);

            $rs->MoveNext();

        }

        /// DIRTY HACK to retrieve all the ' ' (1 space) fields converted back

        /// to '' (empty string) for Oracle. It's the only way to work with

        /// all those NOT NULL DEFAULT '' fields until we definetively delete them

        if ($CFG->dbfamily == 'oracle') {

            array_walk($results, 'onespace2empty');

        }

        /// End of DIRTY HACK

        rs_close($rs);

        return $results;

    } else {

        rs_close($rs);

        return false;

    }

}



/**

 * Set a single field in every table row where all the given fields match the given values.

 *

 * @uses $CFG

 * @uses $db

 * @param string $table The database table to be checked against.

 * @param string $newfield the field to set.

 * @param string $newvalue the value to set the field to.

 * @param string $field1 the first field to check (optional).

 * @param string $value1 the value field1 must have (requred if field1 is given, else optional).

 * @param string $field2 the second field to check (optional).

 * @param string $value2 the value field2 must have (requred if field2 is given, else optional).

 * @param string $field3 the third field to check (optional).

 * @param string $value3 the value field3 must have (requred if field3 is given, else optional).

 * @return mixed An ADODB RecordSet object with the results from the SQL call or false.

 */

function set_field($table, $newfield, $newvalue, $field1, $value1, $field2='', $value2='', $field3='', $value3='') {



    global $CFG;



    // Clear record_cache based on the parameters passed

    // (individual record or whole table)

 …

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