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Building Apps with Go & MySQL

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VividCortex Webinar - Baron Schwartz - November 11, 2014

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About BaronFounder of @VividCortex

Author of High Performance MySQL

@xaprb on Twitter

baron@vividcortex.com

http://www.linkedin.com/in/xaprb

Optimization, Backups, Replication, and more

Baron Schwartz, Peter Zaitsev &

Vadim Tkachenko

High PerformanceMySQL

3rd Edition

Covers Version 5.5

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VividCortex - MySQL Performance Management

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What’s Nice About Go?

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Interfaces

Concurrency primitives

Syntax

Performance

Static Linking

Tools

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What’s Not As Nice?Hard to Google it (use “golang”)

Package versioning (use github.com/VividCortex/johnny-deps/)

Doesn’t have generics (not a big deal)

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Go Database Design Patterns

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Things To KnowWhat is database/sql?

Where is the documentation?

How do I create a database connection?

How do I query a connection?

How do I retrieve results from a query?

What are the common operations?

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Overview of database/sqlA generic, minimal interface for SQL-like databases

Verbs and nouns: Open, Prepare, Exec, Query, QueryRow, Scan, Close

DB, Stmt, Value, Row, Rows, Result

Tx, Begin, Commit, Rollback

Docs: http://golang.org/pkg/database/sql/

Tutorial: http://go-database-sql.org/

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æ9package  main  

import  (     _  "github.com/go-­‐sql-­‐driver/mysql"  

  "database/sql"     "log"  )  

func  main()  {     db,  err  :=  sql.Open("mysql",       "user:password@tcp(127.0.0.1:3306)/test")     if  err  !=  nil  {       log.Println(err)     }     defer  db.Close()  

     //  Do  something  useful  here.  }  

åOne-Shot Query

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  var  str  string     err  =  db.QueryRow(  

"select  hello  from  hello.world  where  id  =  1").Scan(&str)     if  err  !=  nil  &&  err  !=  sql.ErrNoRows  {       log.Println(err)     }     log.Println(str)

åQuery...

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  var  id  int     var  str  string     q  :=  "select  id,  hello  from  hello.world  where  id  =  ?"  

  rows,  err  :=  db.Query(q,  1)     if  err  !=  nil  {       log.Fatal(err)     }        defer  rows.Close()

å... Then Fetch Rows

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  for  rows.Next()  {       err  =  rows.Scan(&id,  &str)       if  err  !=  nil  {         log.Fatal(err)       }       //  Use  the  variables  scanned  from  the  row     }     if  err  =  rows.Err();  err  !=  nil  {       log.Fatal(err)     }  

åPrepare...

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  stmt,  err  :=  db.Prepare(       "select  id,  hello  from  hello.world                where  id  =  ?")     if  err  !=  nil  {       log.Fatal(err)     }        defer  stmt.Close()

å... Then Execute & Fetch

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  rows,  err  :=  stmt.Query(1)     if  err  !=  nil  {       log.Fatal(err)     }        defer  rows.Close()  

  for  rows.Next()  {       //  ...     }  

åInsert...

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  stmt,  err  :=  db.Prepare(       "insert  into  hello.world(hello)  values(?)")     if  err  !=  nil  {       log.Fatal(err)     }        defer  stmt.Close()  

  res,  err  :=  stmt.Exec("hello,  Dolly")     if  err  !=  nil  {       log.Fatal(err)     }

å... And Check Results

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  lastId,  err  :=  res.LastInsertId()     if  err  !=  nil  {       log.Fatal(err)     }     rowCnt,  err  :=  res.RowsAffected()     if  err  !=  nil  {       log.Fatal(err)     }

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Docs: “Pleasantly Lightweight!”

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Connection Pooling

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Big Unsigned Integers

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Unexpected Connections

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åResource Exhaustion

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//  Don’t  do  this!  for  i  :=  0;  i  <  50;  i++  {     _,  err  :=  db.Query("DELETE  FROM  hello.world")  }  

//  Use  this  instead!  for  i  :=  0;  i  <  50;  i++  {     _,  err  :=  db.Exec("DELETE  FROM  hello.world")  }  

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Retry. Retry. Retry. Retry. Retry. Retry. Retry. Retry. Retry. Retry.

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Handling NULLs

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åWorking with NULL

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var  s  sql.NullString  err  :=  db.QueryRow(        "SELECT  name  FROM  foo  WHERE  id=?",        id).Scan(&s)  

if  s.Valid  {        //  use  s.String  }  else  {        //  NULL  value  }  

//  If  you  don’t  care  to  check  whether  it  was  NULL,  //  Just  use  s.String  without  checking,  it’ll  be  ""

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Boilerplate code everywhere

There’s no sql.NullUint64

Nullability is tricky, not future-proof

It’s not very Go-ish (no useful default zero-value)

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NULL Makes Code Ugly

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ORMs - Not Really Suited for Go

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Interfaces - Learn Them, Love Them

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e.g. https://vividcortex.com/blog/2014/11/11/encrypting-data-in-mysql-with-go/

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Resources

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http://golang.org/pkg/database/sql/

http://go-database-sql.org/

https://github.com/go-sql-driver/mysql

http://jmoiron.net/blog/

http://twitter.com/VividCortex/ <--- lots of Go tips

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Questions?baron@vividcortex.com @xaprb • linkedin.com/in/xaprb

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Image Creditshttp://www.flickr.com/photos/simens/6306917636/ http://www.flickr.com/photos/dexxus/5794905716/ http://www.flickr.com/photos/sebastian_bergmann/202396633/ http://www.flickr.com/photos/doug88888/4794114114/ http://www.flickr.com/photos/oatsy40/6443878013/ http://www.sxc.hu/photo/1160562/ Google Maps (screenshot) http://www.flickr.com/photos/estherase/13553883/ http://www.flickr.com/photos/paperpariah/4150220583/ http://www.flickr.com/photos/zooboing/4743616313/ http://www.flickr.com/photos/dseneste/5912382808/ http://www.flickr.com/photos/clickykbd/66165381/sizes/l/ http://www.flickr.com/photos/mamnaimie/5576980406/ https://www.flickr.com/photos/zachstern/87431231

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