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Do not query result cache twice in case of cache miss #4169

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26 changes: 17 additions & 9 deletions lib/Doctrine/DBAL/Cache/ResultCacheStatement.php
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Original file line number Diff line number Diff line change
Expand Up @@ -52,24 +52,29 @@ class ResultCacheStatement implements IteratorAggregate, ResultStatement, Result
/** @var ResultStatement */
private $statement;

/** @var array<string,mixed>|null */
private $fetchedData;

/** @var array<int,array<string,mixed>>|null */
private $data;

/** @var int */
private $defaultFetchMode = FetchMode::MIXED;

/**
* @param string $cacheKey
* @param string $realKey
* @param int $lifetime
* @param string $cacheKey
* @param string $realKey
* @param int $lifetime
* @param array<string,mixed>|null $fetchedData
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@greg0ire greg0ire Jul 22, 2020

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Should this new argument become mandatory in 3.0.x?

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@k0ka k0ka Jul 22, 2020

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I think, yes.
However, the class is renamed to CachingResult in 3.0

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@morozov morozov Jul 23, 2020

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Why don't we implement a proper fix in 3.0.x first and then backport in a BC-way? Otherwise, it's not clear what the new intended logic is.

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@k0ka k0ka Jul 23, 2020

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I don't know how you releasing process is working. I consider this bug as a minor so it doesn't make sense to break backward compatibility.

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@morozov morozov Jul 23, 2020

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Let's at least make it clear in the parameter description that this parameter will be mandatory in 3.0. Otherwise, it's not clear why fetching the data has to be implemented twice.

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@k0ka k0ka Jul 24, 2020

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I feel confused about how to do it all in 2.11.

I have opened the new #4189 for 3.0.x version with BC Break and mandatory $fetchedData field.

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@morozov morozov Jul 24, 2020

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I'm not that well familiar with the design of the caching layer and I still don't get the design: instead of fetching the data from the result, why does the result now use the fetched data and still can fetch from the result via fetch*() methods? Is this still necessary?

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@k0ka k0ka Jul 24, 2020 •
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The result cache is fetched in ResultCacheStatement only if no fetchedData is provided to the constructor. It is done for backward compatibility - someone could use ResultCacheStatement before and it should continue working without the last parameter.

DBAL uses this class only in one place and it always sends fetchedData. So, result cache won't be fetched 2 times if DBAL is used ordinarily.

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@morozov morozov Jul 24, 2020

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The result cache is fetched in ResultCacheStatement only if no fetchedData is provided to the constructor.

Let's then continue the discussion in #4189 where BC is of no concern. The new class still depends on the Result.

*/
public function __construct(ResultStatement $stmt, Cache $resultCache, $cacheKey, $realKey, $lifetime)
public function __construct(ResultStatement $stmt, Cache $resultCache, $cacheKey, $realKey, $lifetime, ?array $fetchedData = null)
{
$this->statement = $stmt;
$this->resultCache = $resultCache;
$this->cacheKey = $cacheKey;
$this->realKey = $realKey;
$this->lifetime = $lifetime;
$this->fetchedData = $fetchedData;
}

/**
Expand Down Expand Up @@ -336,13 +341,16 @@ private function saveToCache(): void
return;
}

$data = $this->resultCache->fetch($this->cacheKey);
if (! $data) {
$data = [];
if ($this->fetchedData === null) {
$this->fetchedData = $this->resultCache->fetch($this->cacheKey);
}

if (! $this->fetchedData) {
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@morozov morozov Jul 23, 2020

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Please avoid implicit conversion to boolean. It's not allowed in newer branches.

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@k0ka k0ka Jul 23, 2020 •
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Ok. This line was written before me - I've just change the variable name.

dbal/lib/Doctrine/DBAL/Cache/ResultCacheStatement.php

Line 340 in 8c9e92a

if (! $data) {

$this->fetchedData = [];
}

$data[$this->realKey] = $this->data;
$this->fetchedData[$this->realKey] = $this->data;

$this->resultCache->save($this->cacheKey, $data, $this->lifetime);
$this->resultCache->save($this->cacheKey, $this->fetchedData, $this->lifetime);
}
}
11 changes: 10 additions & 1 deletion lib/Doctrine/DBAL/Connection.php
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Original file line number Diff line number Diff line change
Expand Up @@ -1207,10 +1207,19 @@ public function executeCacheQuery($sql, $params, $types, QueryCacheProfile $qcp)
} elseif (array_key_exists($realKey, $data)) {
$stmt = new ArrayStatement([]);
}
} else {
$data = [];
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@morozov morozov Jul 23, 2020

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Why is this needed?

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@k0ka k0ka Jul 23, 2020 •
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It is needed to distinguish "data from query cache is not loaded" and "data from query cache is loaded and empty".
This data was be set to empty array in ResultCacheStatement before -

dbal/lib/Doctrine/DBAL/Cache/ResultCacheStatement.php

Line 341 in 8c9e92a

$data = [];

}

if (! isset($stmt)) {
$stmt = new ResultCacheStatement($this->executeQuery($sql, $params, $types), $resultCache, $cacheKey, $realKey, $qcp->getLifetime());
$stmt = new ResultCacheStatement(
$this->executeQuery($sql, $params, $types),
$resultCache,
$cacheKey,
$realKey,
$qcp->getLifetime(),
$data
);
}

$stmt->setFetchMode($this->defaultFetchMode);
Expand Down