Sorry for my poor English. If you can help with improving the English in this documentation, please contact me.
## MyMySQL v1.5.4 (2015-01-08)
This package contains MySQL client API written entirely in Go. It is designed
to work with the MySQL protocol version 4.1 or greater. It definitely works
well with MySQL server version 5.0 and 5.1 (I use these versions of MySQL
servers for my applications). Some people claim that mymysql works with older
versions of MySQL protocol too.
## Changelog
v1.5.4: Bugs fixed in native and godrv packages.
v1.5.3: Bugs fixed in new godrv code.
v1.5.1: Conn.NetConn method added.
v1.5: Needs Go 1.1 (time.ParseInLocation and net.Dialer) to compile.
v1.4: `Stmt.ResetParams`, `Stmt.Map` and `Stmt.NumFields` methods disappeared.
New `Stmt.Fields` method. *godrv* implements `driver.Queryer` interface which
improves performance when compiled with Go tip.
v1.3: Overall performance improved by factor 1.5 to 1.8. All Encode* functions
now accept properly sized `[]byte` slice as first argument.
v1.2: Faster execution of simple queries in *mymysql/godrv*. `EscapeString`
method renamed to `Escape`.
v1.1: Client error codes moved from *mymysql/native* pacage to *mymysql/mysql*.
v1.0: Transactions added to autorc, new Transaction.IsValid method. I think
this library is mature enough to release it as v1.0
v0.4.11: Add Reconnect, Register, SetMaxPktSize, Bind to autorc.
v0.4.10: New *Clone* method for create connection from other connection.
v0.4.9: New method for create connection from configuration in file: *NewFromCF*.
v0.4.8: New methods for obtain only first/last row from result set. Better
implementation of discarding rows in End method.
v0.4.7: ScanRow and MakeRow methods addad. ScanRow is more efficient than GetRow because it doesn't allocate memory for every row received from the server. *godrv* Value.Next method now uses the new ScanRow method.
v0.4.6: StatusOnly method added to mysql.Result.
v0.4.5: New autorc.Conn.PrepareOnce method.
v0.4.4:
1. Row.Int, Row.Uint, Row.Int64, ... methods now panic in case of error.
2. New Row.Float method.
v0.4.3:
1. Fixed issue with panic when the server returns MYSQL_TYPE_NEWDECIMAL.
2. Decimals are returned as float64 (previously they were returned as []byte).
v0.4.2:
1. A lot of changes with MySQL time handling:
- Datetime type replaced by time.Time.
- Time type replaced by time.Duration.
- Support for time.Time type added to godrv.
2. row.Int64/row.Uint64 methods added.
3. Rename BindParams to Bind.
v0.4.1:
BindParams supports Go bool type.
v0.4:
1. Modular design:
- MySQL wire protocol handling moved to *mymysql/native*
- Thread safe wrapper of *native* engine in separate *mymysql/thrsafe*
- *mymysql/mysql* package contains definitions of interfaces to engines and
common (engine-independent) functions.
- Automatic reconnect interface moved to *mymysql/autorc*.
2. *mysql.New* and other functions returns mostly interface types. So all
previously exported members were converted to methods (with except *mysql.Row*
and *mysql.Field* - their definition didn't changed).
3. Transactions added. If you use *mymysql/thrsafe" engine transactions are
fully thread safe.
4. Driver for *exp/sql*.
## Installing
To install all subpackages of *mymysql* you need to get three of them:
$ go get github.com/ziutek/mymysql/thrsafe
$ go get github.com/ziutek/mymysql/autorc
$ go get github.com/ziutek/mymysql/godrv
or just run one command to get all subpackages:
$ go get -v github.com/ziutek/mymysql/...
*go get* automagically selects the proper version of *mymysql* for your Go
release. After this command *mymysql* is ready to use.
## Testing
For testing you will need to create the test database and a test user:
mysql> create database test;
mysql> grant all privileges on test.* to testuser@localhost;
mysql> set password for testuser@localhost = password("TestPasswd9");
Make sure that MySQL *max_allowed_packet* variable in *my.cnf* is equal or greater than 34M (In order to test long packets).
The default MySQL server address is *127.0.0.1:3306*.
Next run tests:
$ cd $GOPATH/src/github.com/ziutek/mymysql
$ ./all.bash test
## Examples
### Example 1
package main
import (
"os"
"github.com/ziutek/mymysql/mysql"
_ "github.com/ziutek/mymysql/native" // Native engine
// _ "github.com/ziutek/mymysql/thrsafe" // Thread safe engine
)
func main() {
db := mysql.New("tcp", "", "127.0.0.1:3306", user, pass, dbname)
err := db.Connect()
if err != nil {
panic(err)
}
rows, res, err := db.Query("select * from X where id > %d", 20)
if err != nil {
panic(err)
}
for _, row := range rows {
for _, col := range row {
if col == nil {
// col has NULL value
} else {
// Do something with text in col (type []byte)
}
}
// You can get specific value from a row
val1 := row[1].([]byte)
// You can use it directly if conversion isn't needed
os.Stdout.Write(val1)
// You can get converted value
number := row.Int(0) // Zero value
str := row.Str(1) // First value
bignum := row.MustUint(2) // Second value
// You may get values by column name
first := res.Map("FirstColumn")
second := res.Map("SecondColumn")
val1, val2 := row.Int(first), row.Str(second)
}
}
If you do not want to load the entire result into memory you may use
*Start* and *GetRow* methods:
res, err := db.Start("select * from X")
checkError(err)
// Print fields names
for _, field := range res.Fields() {
fmt.Print(field.Name, " ")
}
fmt.Println()
// Print all rows
for {
row, err := res.GetRow()
checkError(err)
if row == nil {
// No more rows
break
}
// Print all cols
for _, col := range row {
if col == nil {
fmt.Print("<NULL>")
} else {
os.Stdout.Write(col.([]byte))
}
fmt.Print(" ")
}
fmt.Println()
}
GetRow method allocates a new chunk of memory for every received row. If your
query returns hundreds of rows you should opt for the ScanRow method to avoid
unnecessary allocations:
// Print all rows
row := res.MakeRow()
for {
err := res.ScanRow(row)
if err == io.EOF {
// No more rows
break
}
checkError(err)
// Print all cols
// [...]
}
### Example 2 - prepared statements
You can use *Run* or *Exec* method for prepared statements:
stmt, err := db.Prepare("insert into X values (?, ?)")
checkError(err)
type Data struct {
Id int
Tax *float32 // nil means NULL
}
data = new(Data)
for {
err := getData(data)
if err == endOfData {
break
}
checkError(err)
_, err = stmt.Run(data.Id, data.Tax)
checkError(err)
}
*getData* is the function which retrieves data from somewhere and set *Id* and
*Tax* fields of the Data struct. In the case of *Tax* field *getData* may
assign a pointer the retrieved variable or nil if NULL should be stored in
database.
If you pass parameters to *Run* or *Exec* method, the data is rebound on every
method call. This isn't efficient if the statement will be executed more than once.
You can bind parameters and use *Run* or *Exec* method without parameters, to avoid
these unnecessary rebinds. Warning! If you use *Bind* in multithreaded
applications, you should ensure that no other thread will use *Bind* for the
same statement, until you no longer need bound parameters.
The simplest way to bind parameters is:
stmt.Bind(data.Id, data.Tax)
but you can't use it in our example, because parameters bound this way can't
be changed by *getData* function. You may modify bindings like this:
stmt.Bind(&data.Id, &data.Tax)
and now it should work properly. But in our example there is better solution:
stmt.Bind(data)
If *Bind* method has one parameter, and this parameter is a struct or
a pointer to the struct, it treats all fields of this struct as parameters and
binds them.
This is the improved code of the previous example:
data = new(Data)
stmt.Bind(data)
for {
err := getData(data)
if isEndOfData(error) {
break
}
checkError(err)
_, err = stmt.Run()
checkError(err)
}
### Example 3 - using SendLongData in conjunction with http.Get
_, err = db.Start("CREATE TABLE web (url VARCHAR(80), content LONGBLOB)")
checkError(err)
ins, err := db.Prepare("INSERT INTO web VALUES (?, ?)")
checkError(err)
var url string
ins.Bind(&url, []byte(nil)) // []byte(nil) for properly type binding
for {
// Read URL from stdin
url = ""
fmt.Scanln(&url)
if len(url) == 0 {
// Stop reading if URL is blank line
break
}
// Make a connection
resp, err := http.Get(url)
checkError(err)
// We can retrieve response directly into database because
// the resp.Body implements io.Reader. Use 8 kB buffer.
err = ins.SendLongData(1, resp.Body, 8192)
checkError(err)
// Execute insert statement
_, err = ins.Run()
checkError(err)
}
### Example 4 - multi statement / multi result
res, err := db.Start("select id from M; select name from M")
checkError(err)
// Get result from first select
for {
row, err := res.GetRow()
checkError(err)
if row == nil {
// End of first result
break
}
// Do something with with the data
functionThatUseId(row.Int(0))
}
// Get result from second select
res, err = res.NextResult()
checkError(err)
if res == nil {
panic("Hmm, there is no result. Why?!")
}
for {
row, err := res.GetRow()
checkError(err)
if row == nil {
// End of second result
break
}
// Do something with with the data
functionThatUseName(row.Str(0))
}
### Example 5 - transactions
import (
"github.com/ziutek/mymysql/mysql"
_ "github.com/ziutek/mymysql/thrsafe" // for thread safe transactions
)
// [...]
// Statement prepared before transaction begins
ins, err := db.Prepare("insert A values (?, ?)")
checkError(err)
// Begin a new transaction
tr, err := db.Begin()
checkError(err)
// Now db is locked, so any method that uses db and sends commands to
// MySQL server will be blocked until Commit or Rollback is called.
// Commands in transaction are thread safe to
go func() {
_, err = tr.Start("insert A values (1, 'jeden')")
checkError(err)
} ()
_, err = tr.Start("insert A values (2, 'dwa')")
checkError(err)
// You can't use statements prepared before transaction in the usual way,
// because the connection is locked by the Begin method. You must bind the statement
// to the transaction before using it.
_, err = tr.Do(ins).Run(3, "three")
checkError(err)
// For a greater number of calls
ti := tr.Do(ins)
_, err = ti.Run(4, "four")
checkError(err)
_, err = ti.Run(5, "five")
checkError(err)
// At the end you can Commit or Rollback. tr is invalidated and using it
// after Commit/Rollback will cause a panic.
tr.Commit()
### Example 6 - autoreconn interface
import (
"github.com/ziutek/mymysql/autorc"
_ "github.com/ziutek/mymysql/thrsafe" // You may also use the native engine
)
// [...]
db := autorc.New("tcp", "", "127.0.0.1:3306", user, pass, dbname)
// Initilisation commands. They will be executed after each connect.
db.Register("set names utf8")
// There is no need to explicity connect to the MySQL server
rows, res, err := db.Query("SELECT * FROM R")
checkError(err)
// Now we are connected.
// It does not matter if connection will be interrupted during sleep, eg
// due to server reboot or network down.
time.Sleep(9e9)
// If we can reconnect in no more than db.MaxRetries attempts this
// statement will be prepared.
sel, err := db.Prepare("SELECT name FROM R where id > ?")
checkError(err)
// We can destroy our connection server side
_, _, err = db.Query("kill %d", db.Raw.ThreadId())
checkError(err)
// But it doesn't matter
sel.Bind(2)
rows, res, err = sel.Exec()
checkError(err)
### Example 7 - use database/sql with mymysql driver
import (
"database/sql"
_"github.com/ziutek/mymysql/godrv"
)
// [...]
// Open new connection. The uri need to have the following syntax:
//
// [PROTOCOL_SPECFIIC*]DBNAME/USER/PASSWD
//
// where protocol specific part may be empty (this means connection to
// local server using default protocol). Currently possible forms:
// DBNAME/USER/PASSWD
// unix:SOCKPATH*DBNAME/USER/PASSWD
// unix:SOCKPATH,OPTIONS*DBNAME/USER/PASSWD
// tcp:ADDR*DBNAME/USER/PASSWD
// tcp:ADDR,OPTIONS*DBNAME/USER/PASSWD
//
// OPTIONS can contain comma separated list of options in form:
// opt1=VAL1,opt2=VAL2,boolopt3,boolopt4
// Currently implemented options:
// laddr - local address/port (eg. 1.2.3.4:0)
// timeout - connect timeout in format accepted by time.ParseDuration
// Register initialisation commands
// (workaround, see http://codereview.appspot.com/5706047)
godrv.Register("SET NAMES latin2") // Overrides default utf8
godrv.Register("CREATE TABLE IF NOT EXISTS my_table ( ... )")
// Create a connection handler
db, err := sql.Open("mymysql", "test/testuser/TestPasswd9")
checkErr(err)
// For other information about database/sql see its documentation.
ins, err := db.Prepare("INSERT my_table SET txt=?")
checkErr(err)
res, err := ins.Exec("some text")
checkErr(err)
id, err := res.LastInsertId()
checkErr(err)
checkErr(ins.Close(ins))
rows, err := db.Query("SELECT * FROM go")
checkErr(err)
for rows.Next() {
var id int
var txt string
checkErr(rows.Scan(&id, &txt))
// Do something with id and txt
}
checkErr(db.Close())
### Example 8 - use stored procedures
import (
"github.com/ziutek/mymysql/mysql"
_ "github.com/ziutek/mymysql/thrsafe" // or native
)
// [...]
res, err := my.Start("CALL MyProcedure(1, 2, 3)")
checkErr(err)
// Procedure can return more than one result set so we have to read all
// results up to the result that doesn't include result set (status only
// result).
for !res.StatusOnly() {
rows, err := res.GetRows()
checkErr(err)
useRows(rows)
res, err := res.NextResult()
checkErr(err)
if res == nil {
panic("nil result from procedure")
}
}
### Example 9 - transactions using autorc
import (
"github.com/ziutek/mymysql/autorc"
_ "github.com/ziutek/mymysql/thrsafe" // You may also use the native engine
)
// [...]
db := autorc.New("tcp", "", "127.0.0.1:3306", user, pass, dbname)
var stmt1, stmt2 autorc.Stmt
func updateDb() {
err := db.PrepareOnce(&stmt1, someSQL1)
checkDbErr(err)
err = db.PrepareOnce(&stmt2, someSQL2)
checkDbErr(err)
err = db.Begin(func(tr mysql.Transaction, args ...interface{}) error {
// This function will be called again if returns a recoverable error
s1 := tr.Do(stmt1.Raw)
s2 := tr.Do(stmt2.Raw)
if _, err := s1.Run(); err != nil {
return err
}
if _, err := s2.Run(); err != nil {
return err
}
// You have to commit or rollback before return
return tr.Commit()
})
checkDbErr(err)
}
Additional examples are in *examples* directory.
## Type mapping
In the case of classic text queries, all variables that are sent to the MySQL
server are embedded in the text query. Thus you always convert them to a string and
send them embedded in an SQL query:
rows, res, err := db.Query("select * from X where id > %d", id)
After text query you always receive a text result. Mysql text result
corresponds to *[]byte* type in mymysql. It isn't *string* type due to
avoidance of unnecessary type conversions. You can always convert *[]byte* to
*string* yourself:
fmt.Print(string(rows[0][1].([]byte)))
or using *Str* helper method:
fmt.Print(rows[0].Str(1))
There are other helper methods for data conversion like *Int* or *Uint*:
fmt.Print(rows[0].Int(1))
All three above examples return value received in row 0 column 1. If you prefer
to use the column names, you can use *res.Map* which maps result field names to
corresponding indexes:
name := res.Map("name")
fmt.Print(rows[0].Str(name))
In case of prepared statements, the type mapping is slightly more complicated.
For parameters sent from the client to the server, Go/mymysql types are
mapped for MySQL protocol types as below:
string --> MYSQL_TYPE_STRING
[]byte --> MYSQL_TYPE_VAR_STRING
int8, uint8 --> MYSQL_TYPE_TINY
int16, uint16 --> MYSQL_TYPE_SHORT
int32, uint32 --> MYSQL_TYPE_LONG
int64, uint64 --> MYSQL_TYPE_LONGLONG
int, uint --> protocol integer type which match size of int
bool --> MYSQL_TYPE_TINY
float32 --> MYSQL_TYPE_FLOAT
float64 --> MYSQL_TYPE_DOUBLE
time.Time --> MYSQL_TYPE_DATETIME
mysql.Timestamp --> MYSQL_TYPE_TIMESTAMP
mysql.Date --> MYSQL_TYPE_DATE
time.Duration --> MYSQL_TYPE_TIME
mysql.Blob --> MYSQL_TYPE_BLOB
nil --> MYSQL_TYPE_NULL
The MySQL server maps/converts them to a particular MySQL storage type.
For received results MySQL storage types are mapped to Go/mymysql types as
below:
TINYINT --> int8
UNSIGNED TINYINT --> uint8
SMALLINT --> int16
UNSIGNED SMALLINT --> uint16
MEDIUMINT, INT --> int32
UNSIGNED MEDIUMINT, UNSIGNED INT --> uint32
BIGINT --> int64
UNSIGNED BIGINT --> uint64
FLOAT --> float32
DOUBLE --> float64
DECIMAL --> float64
TIMESTAMP, DATETIME --> time.Time
DATE --> mysql.Date
TIME --> time.Duration
YEAR --> int16
CHAR, VARCHAR, BINARY, VARBINARY --> []byte
TEXT, TINYTEXT, MEDIUMTEXT, LONGTEX --> []byte
BLOB, TINYBLOB, MEDIUMBLOB, LONGBLOB --> []byte
BIT --> []byte
SET, ENUM --> []byte
NULL --> nil
## Big packets
This package can send and receive MySQL data packets that are biger than 16 MB.
This means that you can receive response rows biger than 16 MB and can execute
prepared statements with parameter data bigger than 16 MB without using
SendLongData method. If you want to use this feature you need to change the default
mymysql setting using the *Conn.SetMaxPktSize* method and change
*max_allowed_packet* value in your MySQL server configuration.
## Thread safe engine
If you import "mymysql/thrsafe" engine instead of "mymysql/native" engine all
methods are thread safe, unless the description of the method says something else.
If one thread is calling *Query* or *Exec* method, other threads will be
blocked if they call *Query*, *Start*, *Exec*, *Run* or other method which send
data to the server, until *Query*/*Exec* return in first thread.
If one thread is calling *Start* or *Run* method, other threads will be
blocked if they call *Query*, *Start*, *Exec*, *Run* or other method which send
data to the server, until all results and all rows will be readed from
the connection in first thread.
In most of my web applications I use the *autorecon* interface with *thrsafe* engine.
For any new connection, one gorutine is created. There is one persistant
connection to MySQL server shared by all gorutines. Applications are usually
running on dual-core machines with GOMAXPROCS=2. I use *siege* to test any
application befor put it into production. There is example output from siege:
# siege my.httpserver.pl -c25 -d0 -t 30s
** SIEGE 2.69
** Preparing 25 concurrent users for battle.
The server is now under siege...
Lifting the server siege.. done.
Transactions: 3212 hits
Availability: 100.00 %
Elapsed time: 29.83 secs
Data transferred: 3.88 MB
Response time: 0.22 secs
Transaction rate: 107.68 trans/sec
Throughput: 0.13 MB/sec
Concurrency: 23.43
Successful transactions: 3218
Failed transactions: 0
Longest transaction: 9.28
Shortest transaction: 0.01
## To do
1. Complete documentation
## Known bugs
1. There is MySQL "bug" in the *SUM* function. If you use prepared statements
*SUM* returns *DECIMAL* value, even if you sum integer column. mymysql returns
decimals as *float64* so cast result from sum to integer (or use *Row.Int*)
causes panic.
# Documentation
[mysql](http://godoc.org/pkg/github.com/ziutek/mymysql/mysql)
[native](http://godoc.org/pkg/github.com/ziutek/mymysql/native)
[thrsafe](http://godoc.org/pkg/github.com/ziutek/mymysql/thrsafe)
[autorc](http://godoc.org/pkg/github.com/ziutek/mymysql/autorc)
[godrv](http://godoc.org/pkg/github.com/ziutek/mymysql/godrv)