Commit d8edd556 authored by Eloy Lafuente's avatar Eloy Lafuente Committed by Jakub Kania
Browse files

MDL-49482 sqlsrv: Implement support of Offset/Fetch in SQL Server 2012+

parent 68629452
......@@ -41,6 +41,12 @@ class sqlsrv_native_moodle_database extends moodle_database {
protected $last_error_reporting; // To handle SQL*Server-Native driver default verbosity
protected $temptables; // Control existing temptables (sqlsrv_moodle_temptables object)
protected $collation; // current DB collation cache
/**
* Does the used db version support ANSI way of limiting (2012 and higher)
* @var bool
*/
protected $supportsoffsetfetch;
/** @var array list of open recordsets */
protected $recordsets = array();
......@@ -240,6 +246,10 @@ class sqlsrv_native_moodle_database extends moodle_database {
$this->free_result($result);
$serverinfo = $this->get_server_info();
// Fetch/offset is supported staring from SQL Server 2012.
$this->supportsoffsetfetch = $serverinfo['version'] > '11';
// Connection established and configured, going to instantiate the temptables controller
$this->temptables = new sqlsrv_native_moodle_temptables($this);
......@@ -809,20 +819,37 @@ class sqlsrv_native_moodle_database extends moodle_database {
public function get_recordset_sql($sql, array $params = null, $limitfrom = 0, $limitnum = 0) {
list($limitfrom, $limitnum) = $this->normalise_limit_from_num($limitfrom, $limitnum);
$needscrollable = (bool)$limitfrom; // To determine if we'll need to perform scroll to $limitfrom.
if ($limitfrom or $limitnum) {
if ($limitnum >= 1) { // Only apply TOP clause if we have any limitnum (limitfrom offset is handled later)
$fetch = $limitfrom + $limitnum;
if (PHP_INT_MAX - $limitnum < $limitfrom) { // Check PHP_INT_MAX overflow
$fetch = PHP_INT_MAX;
if (!$this->supportsoffsetfetch) {
if ($limitnum >= 1) { // Only apply TOP clause if we have any limitnum (limitfrom offset is handled later).
$fetch = $limitfrom + $limitnum;
if (PHP_INT_MAX - $limitnum < $limitfrom) { // Check PHP_INT_MAX overflow.
$fetch = PHP_INT_MAX;
}
$sql = preg_replace('/^([\s(])*SELECT([\s]+(DISTINCT|ALL))?(?!\s*TOP\s*\()/i',
"\\1SELECT\\2 TOP $fetch", $sql);
}
} else {
$needscrollable = false; // Using supported fetch/offset, no need to scroll anymore.
$sql = (substr($sql, -1) === ';') ? substr($sql, 0, -1) : $sql;
// We need order by to use FETCH/OFFSET.
// Ordering by first column shouldn't break anything if there was no order in the first place.
if (!strpos(strtoupper($sql), "ORDER BY")) {
$sql .= " ORDER BY 1";
}
$sql .= " OFFSET ".$limitfrom." ROWS ";
if ($limitnum > 0) {
$sql .= " FETCH NEXT ".$limitnum." ROWS ONLY";
}
$sql = preg_replace('/^([\s(])*SELECT([\s]+(DISTINCT|ALL))?(?!\s*TOP\s*\()/i',
"\\1SELECT\\2 TOP $fetch", $sql);
}
}
$result = $this->do_query($sql, $params, SQL_QUERY_SELECT, false, (bool)$limitfrom);
$result = $this->do_query($sql, $params, SQL_QUERY_SELECT, false, $needscrollable);
if ($limitfrom) { // Skip $limitfrom records
if ($needscrollable) { // Skip $limitfrom records.
sqlsrv_fetch($result, SQLSRV_SCROLL_ABSOLUTE, $limitfrom - 1);
}
return $this->create_recordset($result);
......
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