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Merge pull request doctrine#818 from zeroedin-bill/sqlserverlimitfix-2
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Rebuild SQLServerPlatform::doModifyLimitQuery again to use a CTE
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@deeky666
deeky666 committed Dec 15, 2015
2 parents 069280e + f615097 commit de6c0bd
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Showing 3 changed files with 373 additions and 143 deletions.
143 changes: 88 additions & 55 deletions lib/Doctrine/DBAL/Platforms/SQLServerPlatform.php
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Original file line number Diff line number Diff line change
Expand Up @@ -1182,77 +1182,110 @@ protected function doModifyLimitQuery($query, $limit, $offset = null)

$start = $offset + 1;
$end = $offset + $limit;
$orderBy = stristr($query, 'ORDER BY');

//Remove ORDER BY from $query (including nested parentheses in order by list).
$query = preg_replace('/\s+ORDER\s+BY\s+([^()]+|\((?:(?:(?>[^()]+)|(?R))*)\))+/i', '', $query);
// We'll find a SELECT or SELECT distinct and prepend TOP n to it
// Even if the TOP n is very large, the use of a CTE will
// allow the SQL Server query planner to optimize it so it doesn't
// actually scan the entire range covered by the TOP clause.
$selectPattern = '/^(\s*SELECT\s+(?:DISTINCT\s+)?)(.*)$/i';
$replacePattern = sprintf('$1%s $2', "TOP $end");
$query = preg_replace($selectPattern, $replacePattern, $query);

if (stristr($query, "ORDER BY")) {
// Inner order by is not valid in SQL Server for our purposes
// unless it's in a TOP N subquery.
$query = $this->scrubInnerOrderBy($query);
}

$format = 'SELECT * FROM (%s) AS doctrine_tbl WHERE doctrine_rownum BETWEEN %d AND %d ORDER BY doctrine_rownum';
// Build a new limited query around the original, using a CTE
return sprintf(
"WITH dctrn_cte AS (%s) "
. "SELECT * FROM ("
. "SELECT *, ROW_NUMBER() OVER (ORDER BY (SELECT 0)) AS doctrine_rownum FROM dctrn_cte"
. ") AS doctrine_tbl "
. "WHERE doctrine_rownum BETWEEN %d AND %d ORDER BY doctrine_rownum ASC",
$query,
$start,
$end
);
}

// Pattern to match "main" SELECT ... FROM clause (including nested parentheses in select list).
$selectFromPattern = '/^(\s*SELECT\s+(?:(.*)(?![^(]*\))))\sFROM\s/i';
/**
* Remove ORDER BY clauses in subqueries - they're not supported by SQL Server.
* Caveat: will leave ORDER BY in TOP N subqueries.
*
* @param $query
* @return string
*/
private function scrubInnerOrderBy($query)
{
$count = substr_count(strtoupper($query), "ORDER BY");
$offset = 0;

if ( ! $orderBy) {
//Replace only "main" FROM with OVER to prevent changing FROM also in subqueries.
$query = preg_replace(
$selectFromPattern,
'$1, ROW_NUMBER() OVER (ORDER BY (SELECT 0)) AS doctrine_rownum FROM ',
$query,
1
);
while ($count-- > 0) {
$qLen = strlen($query);
$orderByPos = stripos($query, " ORDER BY", $offset);
$parenCount = 0;
$currentPosition = $orderByPos;

return sprintf($format, $query, $start, $end);
}
while ($parenCount >= 0 && $currentPosition < $qLen) {
if ($query[$currentPosition] === '(') {
$parenCount++;
} elseif ($query[$currentPosition] === ')') {
$parenCount--;
}

//Clear ORDER BY
$orderBy = preg_replace('/ORDER\s+BY\s+(.*)/i', '$1', $orderBy);
$orderByParts = explode(',', $orderBy);
$orderByColumns = array();
$currentPosition++;
}

//Split ORDER BY into parts
foreach ($orderByParts as &$part) {
if ($this->isOrderByInTopNSubquery($query, $orderByPos)) {
// If the order by clause is in a TOP N subquery, do not remove
// it and continue iteration from the current position.
$offset = $currentPosition;
continue;
}

if (preg_match('/(([^\s]*)\.)?([^\.\s]*)\s*(ASC|DESC)?/i', trim($part), $matches)) {
$orderByColumns[] = array(
'column' => $matches[3],
'hasTable' => ( ! empty($matches[2])),
'sort' => isset($matches[4]) ? $matches[4] : null,
'table' => empty($matches[2]) ? '[^\.\s]*' : $matches[2]
);
if ($currentPosition < $qLen - 1) {
$query = substr($query, 0, $orderByPos) . substr($query, $currentPosition - 1);
$offset = $orderByPos;
}
}
return $query;
}

$isWrapped = (preg_match('/SELECT DISTINCT .* FROM \(.*\) dctrn_result/', $query)) ? true : false;

$overColumns = array();

//Find alias for each column used in ORDER BY
if ( ! empty($orderByColumns)) {
foreach ($orderByColumns as $column) {
$pattern = sprintf('/%s\.%s\s+(?:AS\s+)?([^,\s)]+)/i', $column['table'], $column['column']);

if ($isWrapped) {
$overColumn = preg_match($pattern, $query, $matches)
? $matches[1] : '';
} else {
$overColumn = preg_match($pattern, $query, $matches)
? ($column['hasTable'] ? $column['table'] . '.' : '') . $column['column']
: $column['column'];
}
/**
* Check an ORDER BY clause to see if it is in a TOP N query or subquery.
*
* @param string $query The query
* @param int $currentPosition Start position of ORDER BY clause
* @return bool true if ORDER BY is in a TOP N query, false otherwise
*/
private function isOrderByInTopNSubquery($query, $currentPosition)
{
// Grab query text on the same nesting level as the ORDER BY clause we're examining.
$subQueryBuffer = '';
$parenCount = 0;

// If $parenCount goes negative, we've exited the subquery we're examining.
// If $currentPosition goes negative, we've reached the beginning of the query.
while ($parenCount >= 0 && $currentPosition >= 0) {
if ($query[$currentPosition] === '(') {
$parenCount--;
} elseif ($query[$currentPosition] === ')') {
$parenCount++;
}

if (isset($column['sort'])) {
$overColumn .= ' ' . $column['sort'];
}
// Only yank query text on the same nesting level as the ORDER BY clause.
$subQueryBuffer = ($parenCount === 0 ? $query[$currentPosition] : " ") . $subQueryBuffer;

$overColumns[] = $overColumn;
}
$currentPosition--;
}

//Replace only first occurrence of FROM with $over to prevent changing FROM also in subqueries.
$over = 'ORDER BY ' . implode(', ', $overColumns);
$query = preg_replace($selectFromPattern, "$1, ROW_NUMBER() OVER ($over) AS doctrine_rownum FROM ", $query, 1);
if (preg_match('/SELECT\s+(DISTINCT\s+)?TOP\s/i', $subQueryBuffer)) {
return true;
}

return sprintf($format, $query, $start, $end);
return false;
}

/**
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