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Building extension of PostgreSQL dialect for JSON support - few questions

Purpose

  • Support for json and jsonb in PHQL for PostgreSQL dialect, I've explained it here:

https://github.com/phalcon/cphalcon/issues/13115

I want to add support only for WHERE conditions, I do not need it for SELECT ... FROM section.

If I succeed, I will pull request in Phalcon incubator.

Current plan / my thought process:

  • Extend current PostgreSQL dialect, like:
  <?php

  namespace inopx\db;

  class InopxPgDialect extends \Phalcon\Db\Dialect\Postgresql {

  ....

inopx is my private namespace of choice.

  • Introduce new expression type json, and detect it, for example:

    \k3\product\K3ProductEntity.title::jsonb <@ '{"name":"Thor"}'

    Where do I start? I mean is there some common funcion where all SQL statements go regardless of using find(), findFirst(), exectute() on Query or Connection Object?

  • Extend getSqlExpression method, and support for new json expression type

    Pass oryginal json expression without modyfying or scanning/validating it to the final SQL Expression.

    Except for modifications of Class properties into valid SQL column name, for example \k3\product\K3ProductEntity.title -> "product"."title"

    But im not sure right now if it will be needed.

  • Is it proper way to add json support for PostgreSQL?

What's more need to / should be done regarding new expression type?

Update: I just got info, that adding new expression type would require update of PHQL parser written in Lemon:

https://github.com/phalcon/cphalcon/tree/master/ext/phalcon/mvc/model/query

as im not familiar with Lemon at all, I will probably give up and create own simple SQL Query Builder or use doctrine + jsonb patch for that matter.

You can always just add it as a function, then just adding dialect extension or extend getSqlExpression will work.

edited 17d ago

Sorry but I doesn't understand

1) add what as a function, and where

2) getSqlExpression as argument is taking preprocessed expressions in form of array containing expression type in expression["type"]

https://github.com/phalcon/cphalcon/blob/master/phalcon/db/dialect.zep - line 256

so i need a way to detect which condition is a JSON/JSONB condition and then pass it to getSqlExpression method in my PostgreSQL dialect class



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Accepted
answer
edited 16d ago

Ok, I've found few older posts regarding dialext extensions and registering functions.

Fortunately Postgresql jsonb operators like <@, or ? can be represented as functions for example jsonb_contains or jsonb_exists.

Now:

$dialect = new \Phalcon\Db\Dialect\Postgresql();
$dialect->registerCustomFunction(
    'jsonb_exists',
    function($dialect, $expression) {
        $arguments = $expression['arguments'];
        return sprintf(
            "jsonb_exists(%s, %s)",
            $dialect->getSqlExpression($arguments[0]),
            $dialect->getSqlExpression($arguments[1])
        );
    }
);
$dialect->registerCustomFunction(
    'jsonb_contains',
    function($dialect, $expression) {
        $arguments = $expression['arguments'];
        return sprintf(
            "jsonb_exists(%s, %s)",
            $dialect->getSqlExpression($arguments[0]),
            $dialect->getSqlExpression($arguments[1])
        );
    }
);

$connection =  new \Phalcon\Db\Adapter\Pdo\Postgresql(array(
  'host' => 'localhost',
  'port' => '5432',
  'dbname' => 'db_name',
  'username' => 'postgres',
  'password' => 'secret',
  'dialectClass' => $dialect
));

// This is working...
$sql2 = 'SELECT * FROM product WHERE jsonb_exists(product."picSmall", \'dataBase64\') LIMIT 1 OFFSET 0;';
$sql2 = 'SELECT * FROM product WHERE jsonb_contains(product."picSmall", \'{"dataBase64":23}\') LIMIT 1 OFFSET 0;';

...and it works like a charm.

But honestly... things like above should be explained in the documentation...