Showing posts with label PHP. Show all posts
Showing posts with label PHP. Show all posts

Tuesday, August 24, 2021

PHP MySQL Connectors -- MySQLi, PDO, and/or X DevAPI

 Help!

I am preparing a presentation for the Longhorn PHP conference titled PHP & MySQL -- How do PDO, MySQLi, and X DevAPI do what they do.  This will be a comparison of using PHP with different MySQL Connectors.  As far as I can tell there are no three way comparisons of mysqli, PDO, and the X DevAPI PECL extension.  And much of the PDO versus myqli stuff looks to me like it has not aged well. 

I have good material in the raw presentation about overall features, parameters for prepared queries. And a good section on the how's and whys on prepared queries.  

But what else would you like to see in such a presentation?  I have read some postings on the web about turning off buffering (fairly simple to do).  But what else are would you like to see compared?

Performance?  Well, my rudimentary and preliminary benchmarks do not really so much of a difference running on the same platform against the data.  But do you know a case where one shines over the others?

Coding style?  Are you more object orientated or procedural?  So you like the you can use the X Protocol to skip having to write structured query language.

So if you have any input on what you would like to see in this presentation PLEASE send it to me!

Sunday, March 10, 2019

MySQL and PHP Basics Part I

I have had some requests to write some blogs on the basics of using PHP and MySQL together.  This will not be a series for the experienced as it will start at a level where I will go into a lot of details but expect very few prerequisites from the reader.  If this is not you, please move on. If it is you and you read something you do not understand, please contact me to show me where I assumed too much.

PHP and MySQL are both in their mid twenties and both vital in the worlds of developers.  With the big improvements in PHP 7 and MySQL 8, I have found a lot of developers flocking to both but stymied by the examples they see as their are many details not explained. So let's get to the explaining!

1. Use the latest software

If you are not using PHP 7.2 or 7.3 (or maybe 7.1) then you are missing out in features and performance.  The PHP 5.x series is deprecated, no longer support, and is quickly disappearing.  

MySQL 8.0 is likewise a big advancement but many sites are using earlier versions.  If you are not on 5.6 with plans to upgrade to 5.7 then you are about to be left behind.  If you are running an earlier version then you are using antique code. Also get your MySQL from MySQL as your Linux distro may not be current, especially for the smaller ones.  The APT and DEB repos can be  found here and there are Docket containers available too. 

In many cases it is a fight to keep your software core tools up to date, or fairly up to to date.  The time and heartache in fighting problems resolved in a later version of software or creating a work around for a feature not in your older version will eventually bite you hard and should be viewed as a CRM (Career Limiting Move).  BTW hiring managers look for folks with current skills not skill for a decade old version of the skills.

2. Do not pick one connector over another (yet!)

PHP is a very rich environment for developers and it has three viable options for connecting to MySQL databases.  Please note that the older mysql connector is deprecated, no longer support, and is to be avoided.  It was replaced by the mysqli or mysqlnd (native driver) and is officially supported by Oracle's MySQL Engineers.  Next is the PDO (public data objects) connector that is designed to be database agnostic but there is no overall maintainer who watches out for the code but Oracle MySQL Engineers do try to fix MySQL related issues if they do not impinge on other PDO code. And the newest, using the new MySQL X DevAPI and X protocol is the X DevAPI connector which supports both SQL and NoSQL interfaces.

The good news for developers is that you can install all three, side by side, with no problem.  For those staring out the ability to transpose from connector can be a little confusing as they work just a bit differently from each other but the ability to use two or more is a good skill to have.  Such much like being able to drive a car with an automatic or manual transmission, it does give you more professional skills.

Next time we will install PHP, MySQL, the three connectors, and some other cool stuff so you can start using PHP to access your MySQL servers.

Wednesday, November 28, 2018

The Symfony Demo Application and MySQL 8

The Symfony Frame work is very popular with PHP developers and it has a very nice Demo Application to help novices learn the intricacies involved. But the demo does not use MySQL. So this blog entry is about re configuring the demo so it works with MySQL 8. And I am using Ubuntu 18.04 LTS to you may have to adjust the following commands to work with your operating system.

This is not difficult but there are some steps that are not exactly self evident that this blog will show you how to get the demo working.  


Preliminaries


The first thing to do is to make sure you have PHP 7.2 or better installed including the php7.2-intl (sudo apt-get install php7.2-intl) package as well as the PDO connector. I will admit I have been using PHP since it appeared and this is the first time I have had to install this package.


And you will want Composer to do the behind the scenes lifting for you and Doctrine to map the relations in the PHP code to the database.  Please see my previous blog on getting Doctrine to work with MySQL 8 (Big hint for the TL;DR crowd, set your .env to DATABASE_URL=mysql://account:password@localhost:3306/databasename ).


You will want to create an account on the MySQL server for use with this demo and then make sure it will have the proper rights to use the new schema.


CREATE USER 'demouser'@'localhost' IDENTIFIED WITH mysql_native_password BY 'S3cr3t#'; 

and  

GRANT ALL on 'databasename'.* to 'demouser'@'localhost'; 


The Demo

Now we can start work on the demo itself. 

The first thing to do in a terminal window is type composer create-project symfony/symfony-demo.  Composer will get the demo code ready for you.  Now cd cymfony-demo.   


Change the .env file (you may have to copy the .env-dist to .env and edit it) as noted above DATABASE_URL=mysql://demouser:S3c3t#@localhost:3306/databasename 

Now it is time to use Doctrine to build create the database, the schemas, and load the data.

$ php bin/console doctrine:database:create
$ php bin/console doctrine:schema:create
$ php bin/console doctrine:fixtures:load


Finally enter php bin/console server:run to start the demo. You will get a notice about the URL to use to get to the demo via a web browser. Use that URL in your web browser to get to the actual demo and below you can see that URL is http://127.0.0.1:8000. 


Symfony Demo started
Running the Symfony Demo Application. Note that the 
application is listening on http:127.0.0.1:8000
Demo in Browser
The Symfony Demo to help you explore this popular PHP Freamwork

Monday, November 19, 2018

Updated: Doctrine and MySQL 8 - An Odd Connection Refused Error

I am currently working my way through the many PHP Frameworks to see how they get on with MySQL 8.  The Frameworks that can take advantage of the MySQL Improved Extension or mysqli can take advantage of the SHA256 Caching Authentication method. But those that are PDO based need to use the older MySQL Native Authentication method.

I wanted to check the PDO based frameworks and today I just happened to be wearing the very nice Symfony shirt I received as part of my presentation at Symfony USA.  So I started with a fresh install of Symfony.  All was going well until it came time to get it to work with MySQL 8 through Doctrine.

Doctrine


Symfony uses Doctrine as an ORM (Object Relational Mapper) and DBAL  (Database Abstraction Layer) as an intermediary to the database.  While I myself am not a big fan of ORMs Doctrine does manage version migration very nicely.  When I tried to tie the frame work and the database together I received a stern connection refused error.

So I double checked the database connection parameters, making sure that I could get to where I wanted using the old MySQL shell.  Yes, the account to be used is identified by the native passwords and I had spelled the account name correctly. Then I double checked for fat-fingering on my part on the .env file where the connection details are stored. Then I did some searching and found someone else had stumbled onto the answer.

What does not work:
DATABASE_URL=mysql://account:password@127.0.0.1:3306/databasename

What does work:
DATABASE_URL=mysql://account:password@localhost:3306/databasename

So a simple s/127.0.0.1/hostname/ got things going.  I double checked the /etc/hosts file to make sure that alias was there (it was).


From then on I was able to create a table with VARCHAR and JSON columns and go about my merry way.

Update: An Oracle MySQL Engineer who works with the PHP connectors informed me that libmysql and all derived clients interpret "localhost" to mean "don't use TCP/ip, but Unix domain socket". And there was a kind post on the Doctrine mailing list informing me that the problems was upstream from Doctrine. Thanks to all who responded to solve this mystery for me.





Wednesday, June 20, 2018

Building the PHP MySQL XDevAPI PECL Extension on MySQL 8.0.11 and PHP 7.2 for the MySQL Document Store

The MySQL Document Store is a NoSQL JSON document store built upon well known MySQL database technology.  PHP runs about eight percent of the Internet.  So putting the two together is a big priority for me. So this blog post is about getting all this together on a Ubuntu 18.04 system.

Note that I will be teaching PHP and the X DevAPI at Oracle Code One and hopefully in some tutorials/workshops this year.  These session will feature the X DevAPI installed on Virtual Box images and I probably will not have time to cover these steps in detail but I will point to this as reference material.


PHP 7.2 

PHP's performance has really skyrocketed with the seven series and the newer betas are looking very impressive.  But to use the new X Devapi you will need to get the shared object for it into your PHP server. 

The MySQL X DevAPI PECL Extension


You can find the MySQL X DevAPI among the many PECL extensions and you can get the latest tarball of source code and also a link to the homepage.  And on that home page are directions for installing/configure the extension. The docs say to do the followings and assume you already have MySQL 8.0.11 installed (or go to https://dev.mysql.com/downloads for the MySQL apt repo software; Install it and then run  sudo apt-get install mysql-shell mysql-server).

$ apt install build-essential libprotobuf-dev libboost-dev openssl protobuf-compiler
$ add-apt-repository ppa:ondrej/php
$ apt install php7.2-cli php7.2-dev php7.2-mysql php7.2-pdo php7.2-xml
$ pecl install mysql_xdevapi

And a quick program to make sure PHP could use the X Devapi.

<?php

$session = mysql_xdevapi\getSession("mysqlx://root:oracle@localhost:33060");
if ($session === NULL ) {
  die("Connection not established!\n");
}

echo "Connection established!\n");

?>

Pretty simple, eh?  Well, I had problems. A call to an undefined function mysql_xdevapi\getSession error.  For some reason the X DevAPI shared object was not being found. 

A Fix

Now there is a way to get things to work but it takes a little work.
1. cd /etc/php/7.2/mods-available
2. cp mysqli.ini mysql_xdevapi.ini
3. edit mysql_xdevapi.ini and change mysqli to mysql_xdevapi on the last line.
4. cd /etc/php/7.2/cli/conf.d
5. ln -s /etc/php/7.2/mods-available/mysql_xdevapi.ini 20-mysql_xdevapi.ini

Now the first test program runs and the Connection established message is displayed!

A Bigger Test


Here is a bigger test program:

 #!/bin/php
<?php

$session = mysql_xdevapi\getSession("mysqlx://root:hidave@localhost:33060");
if ($session === NULL) {
  die("Connection could not be established");
}

$dave = [
  "name" => "Dave",
  "state"  => "TX",
  "category" => 1,
  "job"  => "Community Manager"
];
$alex = [
  "name" => "Alex",
  "age"  => 28,
  "category" => 2,
  "job"  => "House Flipper"
];

$schema = $session->getSchema("test");
$collection = $schema->createCollection("stuff");
$collection = $schema->getCollection("stuff");

$collection->add($alex, $dave)->execute();
var_dump($collection->find("name = 'Dave'")->execute()->fetchOne());
?>


So now we have a working PHP 7.2 with the MySQL XDevAPI PECL extension.  Later we will look into more uses.










Thursday, August 10, 2017

Handy JSON to MySQL Loading Script

JSON in Flat File to MySQL Database

So how do you load that JSON data file into MySQL. Recently I had this question presented to me and I thought I would share a handy script I use to do such work. For this example I will use the US Zip (postal) codes from JSONAR. Download and unzip the file. The data file is named zips.json and it can not be bread directly into MySQL using the SOURCE command. It needs to have the information wrapped in a more palatable fashion.

head zips.json 
{ "city" : "AGAWAM", "loc" : [ -72.622739, 42.070206 ], "pop" : 15338, "state" : "MA", "_id" : "01001" }
{ "city" : "CUSHMAN", "loc" : [ -72.51564999999999, 42.377017 ], "pop" : 36963, "state" : "MA", "_id" : "01002" }
{ "city" : "BARRE", "loc" : [ -72.10835400000001, 42.409698 ], "pop" : 4546, "state" : "MA", "_id" : "01005" }
{ "city" : "BELCHERTOWN", "loc" : [ -72.41095300000001, 42.275103 ], "pop" : 10579, "state" : "MA", "_id" : "01007" }
{ "city" : "BLANDFORD", "loc" : [ -72.936114, 42.182949 ], "pop" : 1240, "state" : "MA", "_id" : "01008" }
{ "city" : "BRIMFIELD", "loc" : [ -72.188455, 42.116543 ], "pop" : 3706, "state" : "MA", "_id" : "01010" }
{ "city" : "CHESTER", "loc" : [ -72.988761, 42.279421 ], "pop" : 1688, "state" : "MA", "_id" : "01011" }
{ "city" : "CHESTERFIELD", "loc" : [ -72.833309, 42.38167 ], "pop" : 177, "state" : "MA", "_id" : "01012" }
{ "city" : "CHICOPEE", "loc" : [ -72.607962, 42.162046 ], "pop" : 23396, "state" : "MA", "_id" : "01013" }
{ "city" : "CHICOPEE", "loc" : [ -72.576142, 42.176443 ], "pop" : 31495, "state" : "MA", "_id" : "01020" }

Follow the Document Store Example

The MySQL Document Store is designed for storing JSON data and this example will follow its practices by having a two column table -- a JSON column, and another column for a primary key (remember InnoDB wants so badly to have a primary key on each table that it will create one for you but it is better practice to make it yourself; besides we want to search on the zipcode which is labeled as _id in the data. So we use a stored generated column that uses JSON_UNQUOTE(JSON_EXTRACT(doc,"$_id")) and saves that info in a column named zip.

So a simple table is created and it looks like this:

mysql> desc zipcode\g
+-------------+-------------+------+-----+---------+-------------------+
| Field       | Type        | Null | Key | Default | Extra             |
+-------------+-------------+------+-----+---------+-------------------+
| doc         | json        | YES  |     | NULL    |                   |
| zip         | char(5)     | NO   | PRI | NULL    | STORED GENERATED  |
+-------------+-------------+------+-----+---------+-------------------+
2 rows in set (0.00 sec)

Handy Script

So now we have the data, we have the table, and now we need to convert the data into something MySQL can use to laod the data.

Bash is one of those shells with so many rich built-in tools that is hard to remember them all. But it does have a hand read line feature that can be used for the task.


#!/bin/bash
file="/home/dstokes/Downloads/zips.json"
while IFS= read line
do
 echo "INSERT INTO zipcode (doc) VALUES ('$line');"
done <"$file"
Run the script and output the data to a file named foo, ./loader.sh > foo. The output shows how the data is wrapped:
$head foo
INSERT INTO zipcode (doc) VALUES ('{ "city" : "AGAWAM", "loc" : [ -72.622739, 42.070206 ], "pop" : 15338, "state" : "MA", "_id" : "01001" }');
INSERT INTO zipcode (doc) VALUES ('{ "city" : "CUSHMAN", "loc" : [ -72.51564999999999, 42.377017 ], "pop" : 36963, "state" : "MA", "_id" : "01002" }');
INSERT INTO zipcode (doc) VALUES ('{ "city" : "BARRE", "loc" : [ -72.10835400000001, 42.409698 ], "pop" : 4546, "state" : "MA", "_id" : "01005" }');
INSERT INTO zipcode (doc) VALUES ('{ "city" : "BELCHERTOWN", "loc" : [ -72.41095300000001, 42.275103 ], "pop" : 10579, "state" : "MA", "_id" : "01007" }');
INSERT INTO zipcode (doc) VALUES ('{ "city" : "BLANDFORD", "loc" : [ -72.936114, 42.182949 ], "pop" : 1240, "state" : "MA", "_id" : "01008" }');
INSERT INTO zipcode (doc) VALUES ('{ "city" : "BRIMFIELD", "loc" : [ -72.188455, 42.116543 ], "pop" : 3706, "state" : "MA", "_id" : "01010" }');
INSERT INTO zipcode (doc) VALUES ('{ "city" : "CHESTER", "loc" : [ -72.988761, 42.279421 ], "pop" : 1688, "state" : "MA", "_id" : "01011" }');
INSERT INTO zipcode (doc) VALUES ('{ "city" : "CHESTERFIELD", "loc" : [ -72.833309, 42.38167 ], "pop" : 177, "state" : "MA", "_id" : "01012" }');
INSERT INTO zipcode (doc) VALUES ('{ "city" : "CHICOPEE", "loc" : [ -72.607962, 42.162046 ], "pop" : 23396, "state" : "MA", "_id" : "01013" }');
INSERT INTO zipcode (doc) VALUES ('{ "city" : "CHICOPEE", "loc" : [ -72.576142, 42.176443 ], "pop" : 31495, "state" : "MA", "_id" : "01020" }');

So now the data can be loaded with mysql -u itisme test < foo.

Tuesday, July 25, 2017

PHP and MySQL Without the SQL

Embedding Structured Query Language (SQL) within PHP, or other programming languages, has been problematic for some. Mixing two programming languages together is just plainly not aesthetically pleasing. Especially when you have a declarative language (SQL) mixed with a procedural-object oriented language. But now, with the MySQL XDevAPI PECL extension, PHP developers can now stop mixing the two languages together together.

MySQL Document Store

The MySQL Document Store eliminates the heavy burden for SQL skills. It is designed to be a high speed, schema-less data store and is based on the MySQL JSON data type. This gives you roughly a gigabyte of store in a document format to do with as needed. So you do not need to architect you data before hand when you have no idea how it will evolve. No need to normalize your data. Now behind the scenes is a power MySQL database server but you are no longer writing SQL to use it!

But Is The Code Ugly?

If you looked at previous editions of this blog then you have seen examples of using the MySQL XDevAPI PECL extension. There is another example below of how to search for the information under various keys in a JSON document. The great news is that the code is all very modern looking PHP with no messy SQL statements thumb-tacked onto the code. This should ongoing support by those with little or no SQL skills.

Previous you would have had to stick SELECT JSON_EXTRACT(doc,'Name') AS 'Country', JSON_EXTRACT(doc,geography) as 'Geo', JSON_EXTACT(doc,'geography.Region) FROM world_x WHERE _id = "USA" as a string in the PHP code. If you prefer the -> operator to replace JSON_EXTRACT, the code can be trimmed down to SELECT doc->"$.Name" AS 'Country', doc->"$.geography" AS 'Geo', doc->"$.geography.Region" FROM world_x WHERE _id = "USA".

But the XDevAPI simplifies these queries into $result = $collection->find('_id = "USA"')->fields(['Name as Country','geography as Geo','geography.Region'])->execute();. This is much easier to understand than the previous two queries for most. And this example shows how to chain down the document path as it specifies all of the geography hey's values and also just the data under geography.Region. It also show how to alias columns from the document store to a label of the developers choice.


#!/usr/bin/php
<?PHP
// Connection parameters
  $user = 'root';
  $passwd = 'hidave';
  $host = 'localhost';
  $port = '33060';
  $connection_uri = 'mysqlx://'.$user.':'.$passwd.'@'.$host.':'.$port; 
  echo $connection_uri . "\n";

// Connect as a Node Session
  $nodeSession = mysql_xdevapi\getNodeSession($connection_uri);
// "USE world_x"
  $schema = $nodeSession->getSchema("world_x");
// Specify collection to use
  $collection = $schema->getCollection("countryinfo");

// Query the Document Store
  $result = $collection->find('_id = "USA"')->fields(['Name as Country','geography as Geo','geography.Region'])->execute();

// Fetch/Display data
  $data = $result->fetchAll();
  var_dump($data);
?>

And The Output


mysqlx://root:hidave@localhost:33060
array(1) {
  [0]=>
  array(3) {
    ["Geo"]=>
    array(3) {
      ["Region"]=>
      string(13) "North America"
      ["Continent"]=>
      string(13) "North America"
      ["SurfaceArea"]=>
      int(9363520)
    }
    ["Country"]=>
    string(13) "United States"
    ["geography.Region"]=>
    string(13) "North America"
  }
}

User Guide

The MySQL Shell User Guide is a great place to start learning how to interactively start using the Document Store.

Tuesday, July 18, 2017

Using find() with the MySQL Document Store

The Video

The find() function for the MySQL Document Store is a very powerful tool and I have just finished a handy introductory video. By the way -- please let me have feed back on the pace, the background music, the CGI special effects (kidding!), and the amount of the content.

The Script

For those who want to follow along with the videos, the core examples are below. The first step is to connect to a MySQL server to talk to the world_x schema (Instructions on loading that schema at the first link above).

\connect root@localhost/world_x

db is an object to points to the world_x schema. To find the records in the countryinfo collection, use db.countryinfo.find(). But that returns 237 JSON documents, too many! So lets cut it down to one record by qualifying that we only want the record where the _id is equal to USA, db.countryinfo.find(‘_id = “USA”’)

Deeper Level items in the Document

You can reach deeper level items by providing the path to the object such as db.countryinfo.find(‘geography.Continent = “North America”). Be sure to remember Case Sensitivity!!

Limits, Offsets, and Specifications

It is very simple to place restrictions on the amount of output by post pending .limit(5).skip(6). And you can specify which parameters meet you specification by using find(‘GNP > 8000000’)

Limiting Fields

But what if you do not want all the document but just a few certain fields. Then post pend .fields([“Name”, “GNP”]) to find().

And once again you can dig deeper into the document with specifying the path, such as.fields([“Name”, “GNP”, “geography.Continent”]).sort(“GNP”).

Sorting

Yes, you can easily sort the output from find() by adding .sort(“GNP”,”Name”) at the end.

More Complex Searches

Of course you can make the find() function perform more complex dives into the data such as db.countryinfo.find(‘GNP> 500000 and IndepYear > 1500”).

Parameter Passed Values

And find of parameter passed values will be happy to find they have not been forgotten. db.countryinfo.find(“Name = :country”).bind(“Country”,”Canada”)

Sunday, July 16, 2017

MySQL Document Store Video Series

I am starting a series of videos on the MySQL Document Store. The Document Store allows those who do not know Structured Query Language (SQL) to use a database without having to know the basics of relational databases, set theory, or data normalization. The goal is to have sort 2-3 minute episodes on the various facets of the Document Store including the basics, using various programming languages (Node.JS, PHP, Python), and materializing free form schemaless, NoSQL data into columns for use with SQL.

The first Episode, Introduction, can be found here.

Please provide feedback and let me know if there are subjects you would want covered in the near future.

Wednesday, June 29, 2016

MySQL Password Security Changes for PHP Developers

MySQL 5.7 introduced many new facets to password security. The first thing most notice is that you are assigned a random root password at installation time. You then have to search the log file for this random password, use it to login, and then change it. For the examples on the post I am using a fresh install of 5.7.13 on Oracle Linux 7.1 and was provided with the easy to remember password of nLvQRk7wq-NY which to me looked like I forgot to hit escape when trying to get out of vim. A quick ALTER USER to change the password and you are on your way.

Defaults

Password Lifetime and Complexity

5.7.13 now has the default password lifetime set to 0 or 'never expire'. My fresh install shows that the value of mysql.user.password_lifetime is set to NULL which means use the server default value. The lifetime is measured in days and stored in the password_last_changed column of the nysql.users table. If the password is expired, you are put into sandbox mode where the only command you can execute is to change the password. That works great for interactive users. But what about your application? It uses a username password pair to talk to the database but it is very unlikely that anyone planned on changing passwords upon expiration. I seriously doubt anyone has set up the exception routine to handle an expired password properly. And if so, how do you notify all involved about this new password --- securely.

What to do

The best thing would be to set the default password lifetime for accounts used by applications to zero. It simply does not expire. QED & out.

But what if your company wants ALL password changed on a regular basis? And they do mean ALL. Earlier there was a listing of the defaults. The test system are set to a password length of eight characters minimum, requires mixed case, requires at least one upper case letter, one special (nonalphanumeric) character, and is of MEDIUM complexity.

MEDIUM complexity means that passwords need one numeric, one lower case, one upper case, and one special character. LOW tests the password length only. And STRONG adds a condition that sub strings of the length of four characters or long do not match entries in a specified password file (use to make sure swear words, common names, etcetera are not part of a password).

Lets create a dummy account.

CREATE USER 'foobar'@'Localhost' IDENTIFIED BY 'Foo@Localhost1' PASSWORD EXPIRE;

Checking the entry in the user table, you will find that the account's password is expired. For extra credit notice what the authentication string is set to. We can't have just a password string as some authentication tokens or hashes are not really password.

So login as foobar and you will get a notice that the password must be reset before we can do anything else.

ALTER USER 'foobar'@'localhost' IDENTIFIED By '1NewP@assword';

Corporate Standard

Your corporate rules may require you to rotate password every N days and set the corresponding complexity. With MySQL 5.7 you can follow what their model is. If you do not have a standard and want to create one, be sure to DOCUMENT well what your standard is and make sure that standard is well known.

There are ways to use packages like PAM or LDAP for authentication but that is for another day.

Monday, April 25, 2016

What happens when you create a MySQL Document Store

The MySQL Document Store introduced with version 5.7.12 allows developers to create document collections without have to know Structured Query Language. The new feature also comes with a new set of terminology. So let us create a collection and see what it in it (basically creating a table for us SQL speakin' old timers).

So start the mysqlsh program, connect to the server, change to the world-x schema (database) switch to Python mode, a create a collection (table).

What did the server do for us? Switching to SQL mode, we can use describe to see what the server has done for us.

We have a two column table. The first is named doc and is used to store JSON. And there is also a column named _id and please notice this column is notated as STORED GENERATED.

The generated column extracts values from a JSON document and materializes that information into a new column that then can be indexed. But what did the system extract for us to create this new column?

Lets use SHOW CREATE TABLE to find out.

mysql-sql> SHOW CREATE TABLE foobar;
+--------+----------------------------------------------------------------------
--------------------------------------------------------------------------------
----------------------------------------------------------------------+
| Table  | Create Table

                                                                      |
+--------+----------------------------------------------------------------------
--------------------------------------------------------------------------------
----------------------------------------------------------------------+
| foobar | CREATE TABLE `foobar` (
  `doc` json DEFAULT NULL,
  `_id` varchar(32) GENERATED ALWAYS AS (json_unquote(json_extract(`doc`,'$._id'
))) STORED NOT NULL,
  UNIQUE KEY `_id` (`_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 |
+--------+----------------------------------------------------------------------
--------------------------------------------------------------------------------
----------------------------------------------------------------------+
1 row in set (0.00 sec)

mysql-sql>
So the 5.7.12 document store is creating an index for us on a field named _id in our JSON document. Hmm, what if I do not have an _id field in my data. So I added two records ("Name" : "Dave" and "Name" : "Jack") into my new collection and then took a peek.
mysql> select * from foobar;
+-------------------------------------------------------------+-----------------
-----------------+
| doc                                                         | _id
                 |
+-------------------------------------------------------------+-----------------
-----------------+
| {"_id": "819a19383d9fd111901100059a3c7a00", "Name": "Dave"} | 819a19383d9fd111
901100059a3c7a00 |
| {"_id": "d639274c3d9fd111901100059a3c7a00", "Name": "Jack"} | d639274c3d9fd111
901100059a3c7a00 |
+-------------------------------------------------------------+-----------------
-----------------+
2 rows in set (0.00 sec)

mysql>

But what if i do have a _id of my own?

The system picked up the _id for the Dexter record. Remember that the index on the _id field is marked UNIQUE which means you can not reuse that number.

So we know the document store wants is creating an unique identification number (that we can also use).

Update: The client generates the identification number, the server can not due to possible conflicts in future sharding projects.

Wednesday, March 23, 2016

Digging Down into JSON data with the MySQL Functions -- A Question from Peter Zaitsev -- Follow Up

Last time this blog covered digging into a JSON document in a MySQL 5.7 table. The goal was to pull certain records matching a particular criteria. Both Peter Zaitsev and Morgan Tocker get my thanks for their kind comments. My example was a little contrived in that an application would be used to fine tune seeking for a particular key value pair. I was trying to pull single records which is kind of silly when it is much easier to use PHP to parse the data. What follows below is a sample PHP script to grab out the matching records and then feed the results, the JSON document, into an array.
#!/usr/bin/php
<?php
$mysqli = new mysqli("localhost", "root", "hidave", "test");

/* check connection */
if (mysqli_connect_errno()) {
    printf("Connect failed: %s\n", mysqli_connect_error());
    exit();
}

$foo = array();
$query0 =
"SELECT* FROM restaurant WHERE json_contains(data, '{\"grade\": \"A\"}', '$.grades')";
echo "$query0\n";
if ($result = $mysqli->query($query0)) {
    $row = $result->fetch_row();
    printf("JSON is %s!\n\n", $row[0]);
    $foo =  json_decode($row[0]);
        var_dump($foo);
} else {
        printf("Errormessage: %s\n", $mysqli->error);

}


$mysqli->close();
In this case we get the data into an array and the the processing is limited to a var_dump().