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Difference between pages "MySQL native client" and "User:EudoraArriaga266"

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==Introduction==
+
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[http://sourceforge.net/projects/erlmysql Erlang client] for MySQl server
+
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is a native client. It means the client is directly connecting to the server and using
+
low level (network socket level) connection protocol. So advantage of the client as a native
+
is speed and performance. Disadvantage is that client design tightly coupled with MySQL
+
connection protocol, but MySQL team is conservative enough with it.
+
  
==Design==
+
Excellent Mario Entire world: Will i even should give this particular flash game an introduction? I [http://www.happywheelz.com/ happy wheels ] think therefore , Mario video game titles are just very fun and excellent time wasters. I've all [http://www.happywheelz.com/ happy wheels ] hours and hours performing Super Mario game titles, take a look at perform it online? Body fat ought to spent cash on Nintendo's creative designers Ds games or whatever ever again, while you can participate in your favourite Mario games immediately from your laptop or computer!
  
The MySQL client is implemented as Erlang/OTP application. Root supervisor of the client
+
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manages a set of datasource processes each of them can be pointed to different MySQl servers
+
or to the same but differently configured. To create a datasource process (or object)
+
we can use function from the client API:
+
<pre>
+
my:new_datasource(my_ds, #datasource{
+
  host = "localhost",
+
  port = 3306,
+
  database = "",
+
  user = "root",
+
  password = "root"}
+
).
+
</pre>
+
Datasource is supervisor in own turn and keeps management under one connection pool process
+
and a few active connection processes to server. The connection pool stores a reusable
+
ip/tcp socket and is tracking their life cycles. When new connection process is creating then the
+
connection pool is trying to provide an existed but idle socket. If set of idle socket is empty
+
connection pool creates new one. If connection process has closed then assigned socket becomes idle
+
and goes to set of idle sockets of the pool.
+
 
+
==Supported features==
+
 
+
The client supports the following client features of MySQL server:
+
* configure client connection using #client_options{} record
+
* compression mode for transfer data through connection
+
* transfer of very long packets as a multi sub-packets
+
* prepared statements execution
+
* transfer a long statement parameters (blob parameters)
+
* fetch cursor on server previously generated by prepared statement
+
* transaction execution
+
 
+
==Getting started==
+
 
+
===Obtain connection===
+
 
+
We have already created datasource object above. So now we can obtain connection to our server:
+
<pre>
+
Conn = my:get_connection(my_ds)
+
</pre>
+
 
+
===Create database===
+
Let's create new database (or schema) on the server:
+
<pre>
+
my:execute_query(Conn, "CREATE DATABASE IF NOT EXISTS testDB")
+
</pre>
+
 
+
===Create table===
+
Next step is a table creation:
+
<pre>
+
my:execute_query(Conn,
+
  "CREATE TABLE testDB.sample_table ("
+
    "id bigint(20) NOT NULL AUTO_INCREMENT,"
+
    "name varchar(45) DEFAULT NULL,"
+
    "PRIMARY KEY (id)"
+
  ") ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8"
+
)
+
</pre>
+
 
+
===Insert and select===
+
 
+
It is time to insert something to new table:
+
<pre>
+
my:execute_query(Conn,
+
  "INSERT INTO testDB.sample_table(name) "
+
  "VALUES ('Alex'), ('John')"
+
)
+
</pre>
+
And finally we can extract this rows from the table:
+
<pre>
+
{Metadata, Rows} = my:execute_query(Conn, "SELECT * FROM testDB.sample_table"),
+
io:format("Result: ~p~n", [Rows])
+
</pre>
+
We can see on console something like this:
+
<pre>
+
Result: [{rs_row_data, [1,"Alex"]},{rs_row_data, [2,"John"]}]
+
</pre>
+
Query returns a tuple that contains two members. First one is metadata record
+
represented information about table fields and second one is list of records represented
+
rows of query result. Each row contains values of fields of SELECT statement. In our case
+
there are 'id' and 'name' fields.
+
 
+
==Prepared statement==
+
 
+
Let's prepare a very simple statement:
+
<pre>
+
Handle = my:get_prepared_statement_handle(
+
  Conn,                                              % - connection handle
+
  "SELECT name FROM testDB.sample_table WHERE id = ?" % - SQL prepared statement with ? placeholders
+
)
+
</pre>
+
The function returns prepared statement handle for followed operations. Now execute it:
+
<pre>
+
{Metadata, Rows} = my:execute_statement(
+
  Conn,                    % - connection handle
+
  Handle,                  % - prepared statement handle
+
  [?MYSQL_TYPE_LONGLONG],  % - list of parameter types
+
  [1]                      % - list of parameter values, corresponded with the statement ? placeholders.
+
),
+
io:format("Result: ~p~n", [Rows])
+
</pre>
+
We need to pass a statement's parameter types and values to function that executes prepared statement. Result has to be:
+
<pre>
+
Result: [{rs_row_data, [1,"Alex"]}]
+
</pre>
+
 
+
==Compressed mode==
+
 
+
Compression protocol is supported by the client if given instance of MySQL supports it.
+
To activate this feature set compress field in #client_options record and pass the record
+
to datasource definition when create new datasource object.
+
<pre>
+
my:new_datasource(
+
  #datasource{
+
    name = my_ds,
+
    host = "localhost",
+
    port = 3306,
+
    database = "",
+
    user = "root",
+
    password = "root",
+
    flags = #client_options{compress=1}
+
  }
+
),
+
Conn = my:get_connection(my_ds)
+
</pre>
+
Then established connection ''Conn'' allows to talk to server with compession.  
+
Note that when we are using compression we win a packets size but lost a processor time.
+
 
+
==Blob transfer==
+
 
+
MySQL client/server protocol allows transfer data for BLOB type field as a separate
+
operation. Suppose we have a column of LONGBLOB type named as longblob_col in our sample_table above:
+
<pre>
+
  CREATE TABLE testDB.sample_table (
+
    id bigint(20) NOT NULL AUTO_INCREMENT,
+
    longblob_col longblob,
+
    name varchar(45) DEFAULT NULL,
+
    PRIMARY KEY (id)
+
  ) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8
+
</pre>
+
And we need to update the field with huge chunk of data. The command is a part of
+
prepared statement execution cycle, so we need prapare statement first:
+
<pre>
+
  Handle = my:get_prepared_statement_handle(Conn,
+
    "UPDATE testDB.sample_table SET longblob_col= ? WHERE id = ?"
+
  )
+
</pre>
+
After that we can send to server long block of data that has size of 1000000 bytes:
+
<pre>
+
my:send_statement_long_parameter(Conn, Handle, 0, &lt;&lt;16#AA:8000000&gt;&gt;),
+
</pre>
+
Third parameter of the function is a position number of given parameter
+
in prepared statement sentence. We can apply the send_statement_long_parameter/4 a few times
+
and all chunks will be merged in one huge data block. Now as we complete a sending
+
of statement parameter value to server we can finally execute the statement:
+
<pre>
+
my:execute_statement(Conn, Handle, [?LONG_BLOB, ?LONG], [null, 1]),
+
</pre>
+
During execution we do not need to send blob parameter value, because it already is in the server.
+
 
+
==Cursor fetch==
+
 
+
After a statement is prepared we can execute it under two modes. First kind of execution
+
is default and immediately returns a result set of the query. Second one
+
does not return a result set but create a cursor on the server side. To retrieve a data from
+
this cursor we can use fetch_statement command like this:
+
<pre>
+
Handle = my:get_prepared_statement_handle(
+
  Conn,
+
  "SELECT * FROM testDB.sample_table WHERE id &lt; ?"
+
),
+
 
+
{Metadata,_} = my:execute_statement(
+
  Conn,
+
  Handle,
+
  [?LONGLONG],
+
  [1],
+
  ?CURSOR_TYPE_READ_ONLY,
+
  true
+
),
+
 
+
{_,R} = my:fetch_statement(Conn, Handle, Metadata, 2),
+
 
+
io:format("Result: ~p~n", [R])
+
</pre>
+
Command to execute the prepared statement in cursor mode and does not return any result but we need
+
get a metadata record for the following command. The next line is a fetch command that return 2
+
first rows from the server side cursor. A fetch command returns only binary packets of result set but
+
skips field metadata. So we have to pass metadata record as a parameter to fetch command
+
due to properly parse rows data. Result has to be:
+
<pre>
+
Result: [{rs_row_data, [2,"John"]}]
+
</pre>
+
 
+
==Author==
+
[[User:Krasnopolski]]
+
 
+
20:57, 30 September 2011 (BST)<br>
+
[[Category:HowTo]]
+
[[Category:Interfacing_Erlang]]
+

Latest revision as of 06:47, 7 November 2012

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The Helicopter Online game: This online game is so simple, yet really incredibly addicting. happy wheels activity is to find the highest rating, which you may comes from surviving over the course that is certainly packed with green obstructs (that'll kill a person if you battle straight into them). Anyone click the computer mouse to go greater and don't whatever it takes to leave the bird drop a bit. This specific game is an excellent video game if you would like possess a little level of competition with your friends to see having the best with game playing.