lampager/lampager

Rapid pagination without using OFFSET

v0.4.2 2021-07-21 16:25 UTC

Requires

• php: ^5.6 || ^7.0 || ^8.0

Requires (Dev)

• codeception/specify: ^0.4.6
• nilportugues/sql-query-formatter: ^1.2.2
• php-coveralls/php-coveralls: ^1.0
• phpunit/phpunit: ^6.4

MIT

• mpyw

• paginator
• pagination
• limit
• offset

README

Lampager Core

The core package of Lampager

Requirements

• PHP: ^5.6 || ^7.0 || ^8.0

Installing

composer require lampager/lampager

Usage

Basically you don't need to directly use this package. For example, if you use Laravel, install lampager/lampager-laravel.

However, you can manually use like this:

use Lampager\Paginator;
use Lampager\ArrayProcessor;

$cursor = [
    'id' => 3,
    'created_at' => '2017-01-10 00:00:00',
    'updated_at' => '2017-01-20 00:00:00',
];

$query = (new Paginator())
    ->forward()
    ->limit(5)
    ->orderByDesc('updated_at') // ORDER BY `updated_at` DESC, `created_at` DESC, `id` DESC
    ->orderByDesc('created_at')
    ->orderByDesc('id')
    ->seekable()
    ->configure($cursor);

$rows = run_your_query_using_PDO($query); // Note: SQLite3 driver example is bundled in the tests/StubPaginator.php. Please refer to that.

$result = (new ArrayProcessor())->process($query, $rows);

It will run the optimized query.

(

    SELECT * FROM `posts`
    WHERE `user_id` = 1
    AND (
        `updated_at` = '2017-01-20 00:00:00' AND `created_at` = '2017-01-10 00:00:00' AND `id` > 3
        OR
        `updated_at` = '2017-01-20 00:00:00' AND `created_at` > '2017-01-10 00:00:00'
        OR
        `updated_at` > '2017-01-20 00:00:00'
    )
    ORDER BY `updated_at` ASC, `created_at` ASC, `id` ASC
    LIMIT 1

) UNION ALL (

    SELECT * FROM `posts`
    WHERE `user_id` = 1
    AND (
        `updated_at` = '2017-01-20 00:00:00' AND `created_at` = '2017-01-10 00:00:00' AND `id` <= 3
        OR
        `updated_at` = '2017-01-20 00:00:00' AND `created_at` < '2017-01-10 00:00:00'
        OR
        `updated_at` < '2017-01-20 00:00:00'
    )
    ORDER BY `updated_at` DESC, `created_at` DESC, `id` DESC
    LIMIT 6

)

And you'll get

object(Lampager\PaginationResult)#1 (5) {
  ["records"]=>
  array(5) {
    [0]=>
    array(5) {
      ["id"]=>
      int(3)
      ["user_id"]=>
      int(1)
      ["text"]=>
      string(3) "foo"
      ["created_at"]=>
      string(19) "2017-01-10 00:00:00"
      ["updated_at"]=>
      string(19) "2017-01-20 00:00:00"
    }
    [1]=>
    array(5) {
      ["id"]=>
      int(5)
      ["user_id"]=>
      int(1)
      ["text"]=>
      string(3) "bar"
      ["created_at"]=>
      string(19) "2017-01-05 00:00:00"
      ["updated_at"]=>
      string(19) "2017-01-20 00:00:00"
    }
    [2]=>
    array(5) {
      ["id"]=>
      int(4)
      ["user_id"]=>
      int(1)
      ["text"]=>
      string(3) "baz"
      ["created_at"]=>
      string(19) "2017-01-05 00:00:00"
      ["updated_at"]=>
      string(19) "2017-01-20 00:00:00"
    }
    [3]=>
    array(5) {
      ["id"]=>
      int(2)
      ["user_id"]=>
      int(1)
      ["text"]=>
      string(3) "qux"
      ["created_at"]=>
      string(19) "2017-01-17 00:00:00"
      ["updated_at"]=>
      string(19) "2017-01-18 00:00:00"
    }
    [4]=>
    array(5) {
      ["id"]=>
      int(1)
      ["user_id"]=>
      int(1)
      ["text"]=>
      string(3) "quux"
      ["created_at"]=>
      string(19) "2017-01-16 00:00:00"
      ["updated_at"]=>
      string(19) "2017-01-18 00:00:00"
    }
  }
  ["hasPrevious"]=>
  bool(false)
  ["previousCursor"]=>
  NULL
  ["hasNext"]=>
  bool(true)
  ["nextCursor"]=>
  array(2) {
    ["updated_at"]=>
    string(19) "2017-01-18 00:00:00"
    ["created_at"]=>
    string(19) "2017-01-14 00:00:00"
    ["id"]=>
    int(6)
  }
}

Question: How about Tuple Comparison?

With this feature, SQL statements should be simpler. However, according to SQL Feature Comparison, some RDBMS, such as SQLServer, do not support this syntax. Therefore, Lampager continuously uses redundant statements.

It is also useful for Doctrine 2 since its DQL lexer does not support the syntax and triggers parse errors.

Classes

Name	Type	Parent Class Implemented Interface	Description
Lampager\Paginator	Class		Fluent factory for building Query
Lampager\AbstractProcessor	Abstract Class		Receive fetched records and format them
Lampager\PaginationResult	Class		Processor wraps result with this by default
Lampager\ArrayProcessor	Class	Lampager\AbstractProcessor	Simple Processor implementation for pure PDO
Lampager\ArrayCursor	Class	Lampager\Contracts\Cursor	Simple Cursor implementation for pure PDO Arrays are automatically wrapped with this
Lampager\Query	Class		SQL configuration container generated by Paginator
Lampager\Query\...	Class		Child components of Query
Lampager\Contracts\Cursor	Interface		Indicates parameters for retrieving previous/next records
Lampager\Contracts\Formatter	Interface		Formatter interface pluggable to Processor
Lampager\Concerns\HasProcessor	Trait		Helper for extended Paginator providing convenient accessibility to Processor

API

Paginator::orderBy()
Paginator::orderByDesc()
Paginator::clearOrderBy()

Add or clear cursor parameter name for ORDER BY statement.
At least one parameter required.

Paginator::orderBy(string $column, string $direction = 'asc'): $this
Paginator::orderByDesc(string $column): $this
Paginator::clearOrderBy(): $this

IMPORTANT: The last key MUST be the primary key.

e.g. $paginator->orderBy('updated_at')->orderBy('id')

Arguments

• (string) $column
  Table column name.
• (string) $direction
  "asc" or "desc".

Paginator::limit()

Define the pagination limit.

Paginator::limit(int $limit): $this

Arguments

• (int) $limit
  Positive integer.

Paginator::forward()
Paginator::backward()

Define the pagination direction.

Paginator::forward(bool $forward = true): $this
Paginator::backward(bool $backward = true): $this

Forward (Default)

    ===============>
[2] [ 3, 4, 5, 6, 7] [8]
 |    |               └ next cursor
 |    └ current cursor
 └ previous cursor

    ===============>
[8] [ 7, 6, 5, 4, 3] [2]
 |    |               └ next cursor
 |    └ current cursor
 └ previous cursor

Backward

    <===============
[2] [ 3, 4, 5, 6, 7] [8]
 |                |   └ next cursor
 |                └ current cursor
 └ previous cursor

    <===============
[8] [ 7, 6, 5, 4, 3] [2]
 |                |   └ next cursor
 |                └ current cursor
 └ previous cursor

IMPORTANT: You need previous cursor to retrieve more results.

Paginator::inclusive()
Paginator::exclusive()

Paginator::inclusive(bool $inclusive = true): $this
Paginator::exclusive(bool $exclusive = true): $this

Change the behavior of handling cursor.

Inclusive (Default)

Current cursor will be included in the current page.

    ===============>
[2] [ 3, 4, 5, 6, 7] [8]
 |    |               └ next cursor
 |    └ current cursor
 └ previous cursor

    <===============
[2] [ 3, 4, 5, 6, 7] [8]
 |                |   └ next cursor
 |                └ current cursor
 └ previous cursor

Exclusive

Current cursor will not be included in the current page.

    ===============>
[2] [ 3, 4, 5, 6, 7] [8]
 |                └ next cursor
 └ current cursor

    <===============
[2] [ 3, 4, 5, 6, 7] [8]
      |               |
      |               └ current cursor
      └ previous cursor

Paginator::unseekable()
Paginator::seekable()

Paginator::unseekable(bool $unseekable = true): $this
Paginator::seekable(bool $seekable = true): $this

Define that the pagination result should contain both of the next cursor and the previous cursor.

• unseekable() always requires one simple SELECT query. (Default)
• seekable() may require SELECT ... UNION ALL SELECT ... query when the cursor parameters are not empty.

Unseekable (Default)

    ===============>
[?] [ 3, 4, 5, 6, 7] [8]
      |               └ next cursor
      └ current cursor

Seekable

    ===============>
[2] [ 3, 4, 5, 6, 7] [8]
 |    |               └ next cursor
 |    └ current cursor
 └ previous cursor

Always when the current cursor parameters are empty

===============>
[ 1, 2, 3, 4, 5] [6]
                  └ next cursor

Paginator::fromArray()

Define options from an associative array.

Paginator::fromArray(array $options): $this

Arguments

• (array) $options
  Associative array that contains the following keys.
  • (int) limit
  • (bool) backward / forward
  • (bool) exclusive / inclusive
  • (bool) seekable / unseekable
  • (string[][]) $orders

e.g.

[
    'limit' => 30,
    'backward' => true,
    'unseekable' => false,
    'orders' => [
        ['created_at', 'asc'],
        ['id', 'asc'],
    ],
]

Paginator::configure()

Generate Query corresponding to the current cursor.

Paginator::configure(Cursor|array $cursor = []): Query

Arguments

• (mixed) $cursor
  An associative array that contains $column => $value or an object that implements \Lampager\Contracts\Cursor. It must be all-or-nothing.
  • For the initial page, omit this parameter or pass an empty array.
  • For subsequent pages, pass all parameters. Partial parameters are not allowed.

AbstractProcessor::process()

Receive a pair of Query and fetched rows to analyze and format them.

AbstractProcessor::process(Query $query, mixed $rows): mixed

Arguments

• (Query) $query
• (mixed) $rows
  Fetched records from database. Typically it should be an array or a Traversable.

Return Value

(mixed)

By default, an instance of \Lampager\PaginationResult is returned. All fields are public.

e.g.

object(Lampager\PaginationResult)#1 (5) {
  ["records"]=>
  array(5) {
    /* ... */
  }
  ["hasPrevious"]=>
  bool(false)
  ["previousCursor"]=>
  NULL
  ["hasNext"]=>
  bool(true)
  ["nextCursor"]=>
  array(2) {
    ["updated_at"]=>
    string(19) "2017-01-18 00:00:00"
    ["created_at"]=>
    string(19) "2017-01-14 00:00:00"
    ["id"]=>
    int(6)
  }
}

Note that

• hasPrevious/hasNext will be false when there are no more results for the corresponding direction.
• Either hasPrevious/hasNext will be null when $cursor is empty or seekable() is not be enabled.

PaginationResult::getIterator()

It can be directly traversed using foreach thanks to the interface \IteratorAggregate.

AbstractProcessor::getIterator(): \ArrayIterator

Return Value

(mixed)

ArrayIterator instance that wraps records.

AbstractProcessor::useFormatter()
AbstractProcessor::restoreFormatter()

Override or restore the formatter for the pagination result.

AbstractProcessor::useFormatter(Formatter|callable $formatter): $this
AbstractProcessor::restoreFormatter(): $this

Callable Formatter Example

<?php

use Lampager\Query;
use Lampager\ArrayProcessor;
use Lampager\PaginationResult;

$formatter = function ($rows, array $meta, Query $query) {
    // Drop table prefix in meta properties (e.g. "posts.updated_at" -> "updated_at")
    foreach (array_filter($meta, 'is_array') as $property => $cursor) {
        foreach ($cursor as $column => $field) {
            unset($meta[$property][$column]);
            $segments = explode('.', $column);
            $meta[$property][end($segments)] = $field;
        }
    }
    return new PaginationResult($rows, $meta);
};

$result = (new ArrayProcessor())->useFormatter($formatter)->process($query, $rows);

Class Formatter Example

<?php

use Lampager\Query;
use Lampager\ArrayProcessor;
use Lampager\PaginationResult;
use Lampager\Contracts\Formatter;

class DropTablePrefix implements Formatter
{
    public function format($rows, array $meta, Query $query)
    {
        // Drop table prefix in meta properties (e.g. "posts.updated_at" -> "updated_at")
        foreach (array_filter($meta, 'is_array') as $property => $cursor) {
            foreach ($cursor as $column => $field) {
                unset($meta[$property][$column]);
                $segments = explode('.', $column);
                $meta[$property][end($segments)] = $field;
            }
        }
        return new PaginationResult($rows, $meta);
    }
}

$result = (new ArrayProcessor())->useFormatter(DropTablePrefix::class)->process($query, $rows);

AbstractProcessor::setDefaultFormatter()
AbstractProcessor::restoreDefaultFormatter()

Globally override or restore the formatter.

static AbstractProcessor::setDefaultFormatter(Formatter|callable $formatter): void
static AbstractProcessor::restoreDefaultFormatter(): void

Example (Laravel)

<?php

use Illuminate\Database\Eloquent\Builder;
use Lampager\Query;
use Lampager\Laravel\Processor as IlluminateProcessor;

IlluminateProcessor::setDefaultFormatter(function ($rows, array $meta, Query $query) {

   // Note:
   //    $builder is provided from extended Paginator.
   //    For example, lampager/lampager-laravel provides QueryBuilder, EloquentBuilder or Relation.
   $builder = $query->builder();

   switch ($builder instanceof Builder ? $builder->getModel() : null) {

       case Post::class:
           return (new PostFormatter())->format($rows, $meta, $query);

       case Comment::class:
           return (new CommentFormatter())->format($rows, $meta, $query);

       default:
           return new PaginationResult($rows, $meta);
   }
});

$posts = Post::lampager()->orderBy('created_at')->orderBy('id')->paginate();
$comments = Comment::lampager()->orderBy('created_at')->orderBy('id')->paginate();