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Add support for LOCK and UNLOCK Statements
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Signed-off-by: Deven Bansod <devenbansod.bits@gmail.com>
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@devenbansod
devenbansod committed Dec 22, 2018
1 parent e07403c commit 09faf92
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203 changes: 203 additions & 0 deletions src/Components/LockExpression.php
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@@ -0,0 +1,203 @@
<?php

/**
* Parses a reference to a LOCK expression.
*/

namespace PhpMyAdmin\SqlParser\Components;

use PhpMyAdmin\SqlParser\Component;
use PhpMyAdmin\SqlParser\Parser;
use PhpMyAdmin\SqlParser\Token;
use PhpMyAdmin\SqlParser\TokensList;

/**
* Parses a reference to a LOCK expression.
*
* @category Components
*
* @license https://www.gnu.org/licenses/gpl-2.0.txt GPL-2.0+
*/
class LockExpression extends Component
{
/**
* The table to be locked.
*
* @var Expression
*/
public $table;

/**
* The type of lock to be applied.
*
* @var string
*/
public $type;

/**
* @param Parser $parser the parser that serves as context
* @param TokensList $list the list of tokens that are being parsed
* @param array $options parameters for parsing
*
* @return CaseExpression
*/
public static function parse(Parser $parser, TokensList $list, array $options = array())
{
$ret = new self();

/**
* The state of the parser.
*
* Below are the states of the parser.
*
* 0 ---------------- [ tbl_name ] -----------------> 1
* 1 ---------------- [ lock_type ] ----------------> 2
* 2 -------------------- [ , ] --------------------> break
*
* @var int
*/
$state = 0;

$prevToken = null;

for (; $list->idx < $list->count; ++$list->idx) {
/**
* Token parsed at this moment.
*
* @var Token
*/
$token = $list->tokens[$list->idx];

// End of statement.
if ($token->type === Token::TYPE_DELIMITER
|| ($token->type === Token::TYPE_OPERATOR
&& $token->value === ',')
) {
break;
}

if ($state === 0) {
$ret->table = Expression::parse($parser, $list, array('parseField' => 'table'));
$state = 1;
} elseif ($state === 1) {
// parse lock type
$ret->type = self::parseLockType($parser, $list);
$state = 2;
}
$prevToken = $token;
}

// 2 is the only valid end state
if ($state !== 2) {
$parser->error('Unexpected end of LOCK expression.', $prevToken);
}

--$list->idx;

return $ret;
}

/**
* @param LockExpression|LockExpression[] $component the component to be built
* @param array $options parameters for building
*
* @return string
*/
public static function build($component, array $options = array())
{
if (is_array($component)) {
return implode(', ', $component);
}

return $component->table . ' ' . $component->type;
}

private static function parseLockType(Parser $parser, TokensList $list) {
$lockType = '';

/**
* The state of the parser while parsing for lock type.
*
* Below are the states of the parser.
*
* 0 ---------------- [ READ ] -----------------> 1
* 0 ------------- [ LOW_PRIORITY ] ------------> 2
* 0 ---------------- [ WRITE ] ----------------> 3
* 1 ---------------- [ LOCAL ] ----------------> 3
* 2 ---------------- [ WRITE ] ----------------> 3
*
* @var int
*/
$state = 0;

$prevToken = null;

for (; $list->idx < $list->count; ++$list->idx) {
/**
* Token parsed at this moment.
*
* @var Token
*/
$token = $list->tokens[$list->idx];

// End of statement.
if ($token->type === Token::TYPE_DELIMITER
|| ($token->type === Token::TYPE_OPERATOR
&& $token->value === ',')
) {
--$list->idx;
break;
}

// Skipping whitespaces and comments.
if ($token->type === Token::TYPE_WHITESPACE || $token->type === Token::TYPE_COMMENT) {
continue;
}

// We only expect keywords
if ($token->type !== Token::TYPE_KEYWORD) {
$parser->error('Unexpected token.', $token);
break;
}

if ($state === 0) {
if ($token->keyword === 'READ') {
$state = 1;
} elseif ($token->keyword === 'LOW_PRIORITY') {
$state = 2;
} elseif ($token->keyword === 'WRITE') {
$state = 3;
} else {
$parser->error('Unexpected keyword.', $token);
break;
}
$lockType .= $token->keyword;
} elseif ($state === 1) {
if ($token->keyword === 'LOCAL') {
$lockType .= ' ' . $token->keyword;
$state = 3;
} else {
$parser->error('Unexpected keyword.', $token);
break;
}
} elseif ($state === 2) {
if ($token->keyword === 'WRITE') {
$lockType .= ' ' . $token->keyword;
$state = 3; // parsing over
} else {
$parser->error('Unexpected keyword.', $token);
break;
}
}

$prevToken = $token;
}

// Only two possible end states
if ($state !== 1 && $state !== 3) {
$parser->error('Unexpected end of Lock expression.', $prevToken);
}

return $lockType;
}
}
5 changes: 5 additions & 0 deletions src/Parser.php
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Expand Up @@ -88,6 +88,11 @@ class Parser extends Core
'START TRANSACTION' => 'PhpMyAdmin\\SqlParser\\Statements\\TransactionStatement',

'PURGE' => 'PhpMyAdmin\\SqlParser\\Statements\\PurgeStatement',

// Lock statements
// https://dev.mysql.com/doc/refman/5.7/en/lock-tables.html
'LOCK' => 'PhpMyAdmin\\SqlParser\\Statements\\LockStatement',
'UNLOCK' => 'PhpMyAdmin\\SqlParser\\Statements\\LockStatement',
);

/**
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128 changes: 128 additions & 0 deletions src/Statements/LockStatement.php
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<?php

/**
* `LOCK` statement.
*/

namespace PhpMyAdmin\SqlParser\Statements;

use PhpMyAdmin\SqlParser\Components\LockExpression;
use PhpMyAdmin\SqlParser\Parser;
use PhpMyAdmin\SqlParser\Statement;
use PhpMyAdmin\SqlParser\Token;
use PhpMyAdmin\SqlParser\TokensList;

/**
* `LOCK` statement.
*
* @category Statements
*
* @license https://www.gnu.org/licenses/gpl-2.0.txt GPL-2.0+
*/
class LockStatement extends Statement
{
/**
* Tables with their Lock expressions.
*
* @var LockExpression[]
*/
public $locked = array();

/**
* Whether it's a LOCK statement
* if false, it's an UNLOCK statement
*/
public $isLock = true;

/**
* @param Parser $parser the instance that requests parsing
* @param TokensList $list the list of tokens to be parsed
*/
public function parse(Parser $parser, TokensList $list)
{
if ($list->tokens[$list->idx]->value === 'UNLOCK') {
// this is in fact an UNLOCK statement
$this->isLock = false;
}
++$list->idx; // Skipping `LOCK`.

/**
* The state of the parser.
*
* Below are the states of the parser.
*
* 0 ---------------- [ TABLES ] -----------------> 1
* 1 -------------- [ lock_expr ] ----------------> 2
* 2 ------------------ [ , ] --------------------> 1
*
* @var int
*/
$state = 0;

/**
* Previous parsed token
*/
$prevToken = null;

for (; $list->idx < $list->count; ++$list->idx) {
/**
* Token parsed at this moment.
*
* @var Token
*/
$token = $list->tokens[$list->idx];

// End of statement.
if ($token->type === Token::TYPE_DELIMITER) {
break;
}

// Skipping whitespaces and comments.
if (($token->type === Token::TYPE_WHITESPACE) || ($token->type === Token::TYPE_COMMENT)) {
continue;
}

if ($state === 0) {
if ($token->type === Token::TYPE_KEYWORD) {
if ($token->keyword !== 'TABLES') {
$parser->error('Unexpected keyword.', $token);
break;
}
$state = 1;
continue;
} else {
$parser->error('Unexpected token.', $token);
break;
}
} elseif ($state === 1) {
if (!$this->isLock) {
// UNLOCK statement should not have any more tokens
$parser->error('Unexpected token.', $token);
break;
}
$this->locked[] = LockExpression::parse($parser, $list);
$state = 2;
} elseif ($state === 2) {
if ($token->value === ',') {
// move over to parsing next lock expression
$state = 1;
}
}

$prevToken = $token;
}

if ($state !== 2 && $prevToken != null) {
$parser->error('Unexpected end of LOCK statement.', $prevToken);
}
}

/**
* @return string
*/
public function build()
{
return trim(($this->isLock ? 'LOCK' : 'UNLOCK')
. ' TABLES ' . LockExpression::build($this->locked));
}
}

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