Best practice: Import mySQL file in PHP; split queries

Question

I have a situation where I have to update a web site on a shared hosting provider. The site has a CMS. Uploading the CMS's files is pretty straightforward using FTP.

I also have to import a big (relative to the confines of a PHP script) database file (Around 2-3 MB uncompressed). Mysql is closed for access from the outside, so I have to upload a file using FTP, and start a PHP script to import it. Sadly, I do not have access to the mysql command line function so I have to parse and query it using native PHP. I also can't use LOAD DATA INFILE. I also can't use any kind of interactive front-end like phpMyAdmin, it needs to run in an automated fashion. I also can't use mysqli_multi_query().

Does anybody know or have a already coded, simple solution that reliably splits such a file into single queries (there could be multi-line statements) and runs the query. I would like to avoid to start fiddling with it myself due to the many gotchas that I'm likely to come across (How to detect whether a field delimiter is part of the data; how to deal with line breaks in memo fields; and so on). There must be a ready made solution for this.

Answer 1

Here is a memory-friendly function that should be able to split a big file in individual queries without needing to open the whole file at once:

function SplitSQL($file, $delimiter = ';')
{
    set_time_limit(0);

    if (is_file($file) === true)
    {
        $file = fopen($file, 'r');

        if (is_resource($file) === true)
        {
            $query = array();

            while (feof($file) === false)
            {
                $query[] = fgets($file);

                if (preg_match('~' . preg_quote($delimiter, '~') . '\s*$~iS', end($query)) === 1)
                {
                    $query = trim(implode('', $query));

                    if (mysql_query($query) === false)
                    {
                        echo '<h3>ERROR: ' . $query . '</h3>' . "\n";
                    }

                    else
                    {
                        echo '<h3>SUCCESS: ' . $query . '</h3>' . "\n";
                    }

                    while (ob_get_level() > 0)
                    {
                        ob_end_flush();
                    }

                    flush();
                }

                if (is_string($query) === true)
                {
                    $query = array();
                }
            }

            return fclose($file);
        }
    }

    return false;
}

I tested it on a big phpMyAdmin SQL dump and it worked just fine.

---

Some test data:

CREATE TABLE IF NOT EXISTS "test" (
    "id" INTEGER PRIMARY KEY AUTOINCREMENT,
    "name" TEXT,
    "description" TEXT
);

BEGIN;
    INSERT INTO "test" ("name", "description")
    VALUES (";;;", "something for you mind; body; soul");
COMMIT;

UPDATE "test"
    SET "name" = "; "
    WHERE "id" = 1;

And the respective output:

SUCCESS: CREATE TABLE IF NOT EXISTS "test" ( "id" INTEGER PRIMARY KEY AUTOINCREMENT, "name" TEXT, "description" TEXT );
SUCCESS: BEGIN;
SUCCESS: INSERT INTO "test" ("name", "description") VALUES (";;;", "something for you mind; body; soul");
SUCCESS: COMMIT;
SUCCESS: UPDATE "test" SET "name" = "; " WHERE "id" = 1;

Answer 2

Single page PHPMyAdmin - Adminer - Just one PHP script file. check : http://www.adminer.org/en/

Answer 3

When StackOverflow released their monthly data dump in XML format, I wrote PHP scripts to load it into a MySQL database. I imported about 2.2 gigabytes of XML in a few minutes.

My technique is to prepare() an INSERT statement with parameter placeholders for the column values. Then use XMLReader to loop over the XML elements and execute() my prepared query, plugging in values for the parameters. I chose XMLReader because it's a streaming XML reader; it reads the XML input incrementally instead of requiring to load the whole file into memory.

You could also read a CSV file one line at a time with fgetcsv().

If you're inporting into InnoDB tables, I recommend starting and committing transactions explicitly, to reduce the overhead of autocommit. I commit every 1000 rows, but this is arbitrary.

I'm not going to post the code here (because of StackOverflow's licensing policy), but in pseudocode:

connect to database
open data file
PREPARE parameterizes INSERT statement
begin first transaction
loop, reading lines from data file: {
    parse line into individual fields
    EXECUTE prepared query, passing data fields as parameters
    if ++counter % 1000 == 0,
        commit transaction and begin new transaction
}
commit final transaction

Writing this code in PHP is not rocket science, and it runs pretty quickly when one uses prepared statements and explicit transactions. Those features are not available in the outdated mysql PHP extension, but you can use them if you use mysqli or PDO_MySQL.

I also added convenient stuff like error checking, progress reporting, and support for default values when the data file doesn't include one of the fields.

I wrote my code in an abstract PHP class that I subclass for each table I need to load. Each subclass declares the columns it wants to load, and maps them to fields in the XML data file by name (or by position if the data file is CSV).