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Distinct in the QueryBuilder #3340

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Distinct in the QueryBuilder #3340

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efd2795
Add functionality to generate distinct queries using the DBAL query b…
michaelcullum Nov 7, 2018
32674ae
Fix CS violations
michaelcullum Nov 7, 2018
118662d
Add tests for distinct functionality
michaelcullum Nov 7, 2018
6105a00
Remove extraneous space for CS
michaelcullum Nov 7, 2018
40a39aa
Add flag to enable setting distinct back to false again
michaelcullum Nov 7, 2018
9b644e1
Add return type hint
michaelcullum Nov 12, 2018
257d5bf
Fix CS
michaelcullum Nov 12, 2018
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34 changes: 33 additions & 1 deletion lib/Doctrine/DBAL/Query/QueryBuilder.php
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Original file line number Diff line number Diff line change
Expand Up @@ -125,6 +125,13 @@ class QueryBuilder
*/
private $boundCounter = 0;

/**
* Whether or not to include a distinct flag in the SELECT clause
*
* @var bool
*/
private $isDistinct = false;

/**
* Initializes a new <tt>QueryBuilder</tt>.
*
Expand Down Expand Up @@ -396,6 +403,31 @@ public function getMaxResults()
return $this->maxResults;
}

/**
* Sets the flag to only retrieve distinct results
*
* @param bool $isDistinct Set true to add the distinct flag, set to false to remove it
*
* @return $this This QueryBuilder instance.
*/
public function distinct($isDistinct = true)
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@morozov morozov Nov 7, 2018

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The API would be cleaner if instead of distinct(false), a developer could call nonDistinct(). Otherwise, it looks sort of asymmetric: distinct() ↔ distinct(false).

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@IonBazan IonBazan Nov 8, 2018

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I think he is trying to make it consistent with Doctrine ORM's QueryBuilder: https://github.com/doctrine/doctrine2/blob/6dc46e78ccf4fe75c80884e7abe41b811f2204b6/lib/Doctrine/ORM/QueryBuilder.php#L765

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@morozov morozov Nov 8, 2018

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We can make it better and improve the ORM’s builder later.

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@michaelcullum michaelcullum Nov 12, 2018 •
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I'm inclined to disagree, the main reason was for consistency with the ORM but I think the ORM behaviour makes sense.

The method is essentially a boolean setter and the most common thing it's being set to is true so the fact it defaults to true is just to make it nicer to use ($qb->distinct() instead of a regularly superfluous true). Assuming you don't rely on the default added for DX it is symmetric: distinct(true) ↔ distinct(false)

It also means you could pass a statement straight into the argument e.g. $qb->distinct($this->myBooleanFlag) should you so wish instead of if ($this->myBooleanFlag) { $qb->distinct(); } else { $qb->nonDistinct(); }.

Finally, DX again, a method called nonDistinct() is much less likely to actually be found by a developer compared to distinct(bool $flag), particularly inflated by the fact that is the ORM's behaviour.

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@morozov morozov Nov 12, 2018 •
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It's not a setter. It's a set of builder commands which you will call or not call depending on the flag and the previous state. If this justification was valid, then instead of assertEquals() and assertNotEquals(), we'd see something like assertIfEquals(bool $equals) in xUnit frameworks.

{
$this->state = self::STATE_DIRTY;
$this->isDistinct = $isDistinct;

return $this;
}

/**
* Returns whether or not the query object is set to return only distinct results
*
* @return bool
*/
public function isDistinct()
{
return $this->isDistinct;
}

/**
* Either appends to or replaces a single, generic query part.
*
Expand Down Expand Up @@ -1099,7 +1131,7 @@ public function resetQueryPart($queryPartName)
*/
private function getSQLForSelect()
{
$query = 'SELECT ' . implode(', ', $this->sqlParts['select']);
$query = 'SELECT' . ($this->isDistinct ? ' DISTINCT ' : ' ') . implode(', ', $this->sqlParts['select']);

$query .= ($this->sqlParts['from'] ? ' FROM ' . implode(', ', $this->getFromClauses()) : '')
. ($this->sqlParts['where'] !== null ? ' WHERE ' . ((string) $this->sqlParts['where']) : '')
Expand Down
30 changes: 30 additions & 0 deletions tests/Doctrine/Tests/DBAL/Query/QueryBuilderTest.php
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Original file line number Diff line number Diff line change
Expand Up @@ -62,6 +62,17 @@ public function testSelectWithSimpleWhere()
self::assertEquals('SELECT u.id FROM users u WHERE u.nickname = ?', (string) $qb);
}

public function testSelectWithDistinct()
{
$qb = new QueryBuilder($this->conn);

$qb->select('u.id')
->from('users', 'u')
->distinct();

self::assertEquals('SELECT DISTINCT u.id FROM users u', (string) $qb);
}

public function testSelectWithLeftJoin()
{
$qb = new QueryBuilder($this->conn);
Expand Down Expand Up @@ -576,6 +587,25 @@ public function testSetFirstResult()
self::assertEquals(10, $qb->getFirstResult());
}

public function testSetDistinct()
{
$qb = new QueryBuilder($this->conn);
$qb->distinct();

self::assertEquals(QueryBuilder::STATE_DIRTY, $qb->getState());
self::assertTrue($qb->isDistinct());
}

public function testSetDistinctFalse()
{
$qb = new QueryBuilder($this->conn);
$qb->distinct(true);
$qb->distinct(false);

self::assertEquals(QueryBuilder::STATE_DIRTY, $qb->getState());
self::assertFalse($qb->isDistinct());
}

public function testResetQueryPart()
{
$qb = new QueryBuilder($this->conn);
Expand Down