sqlbind

sqlbind

sqlbind is a set of database/sql helpers to remove a lot of boilerplate code while always using standard database/sql calls.

It adds :

• Named parameters,
• Binding named parameters to structs,
• Binding structs to sql.Row/sql.Rows results,
• Variables in SQL queries.

sqlbind generates as little SQL code as possible, letting you fine tune your SQL requests.

Named parameters

Basic usage, using maps :

sql, args, err := sqlbind.Named("SELECT * FROM example WHERE name=:name", map[string]interface{}{"name":"foo"})
rows, err := db.Query(sql, args...)

Automatic IN clause expansion :

sqlbind.Named("SELECT * FROM example WHERE name IN(:name)", map[string]interface{}{"name":[]string{"foo", "bar"}})

Variable args :

sqlbind.Named("INSERT INTO example (::names) VALUES(::values)", map[string]interface{}{"name":"foo"}'})
sqlbind.Named("UPDATE example SET ::name=::value", map[string]interface{}{"name":"foo"}'})

Structs, using tags to define DB field names :

type Example struct {
	Name string `db:"name"`
}
e := Example{Name: "foo"}
sqlbind.Named("SELECT * FROM example WHERE name=:name", e)

Add args to a struct (e.g. from query string parameters) :

sqlbind.Named("SELECT * FROM example WHERE name=:name AND domain=:domain", e, sqlbind.Args("domain", "example.com"))

Named placeholders are automatically translated to the right driver-dependant placeholder : ? for MySQL (default style)

sqlbind.SetStyle(sqlbind.MySQL)

or $N for PostgreSQL

sqlbind.SetStyle(sqlbind.PostgreSQL)

Colons inside quotes are ignored and do not need to be escaped (":value" will neither be rewritten neither considered a named parameter), but otherwise need to be doubled (::value will be rewritten to :value but not be considered a named parameter).

Controlling ::names and ::name=::value

Not all fields need to be expanded by ::names and ::name=::value.

This can be achieved using an optional parameter to sqlbin.Named :

sqlbind.Named("INSERT INTO example (::names) VALUES(::values)", map[string]interface{}{"id": 42, "name":"foo"}'}, sqlbind.Only("name"))
sqlbind.Named("INSERT INTO example (::names) VALUES(::values)", map[string]interface{}{"id": 42, "name":"foo"}'}, sqlbind.Exclude("id"))

or using struct tags (better performance) :

type Example struct {
	ID   int    `db:"id,ro"` // will not be expanded by ::names and ::name=::value
}

Variables

Additional variables can be added to SQL queries :

sqlbind.Named("SELECT /* {comment} */ * FROM {table_prefix}example WHERE name=:name", e, sqlbind.Variables("comment", "foo", "table_prefix", "bar_"))

Braces inside quotes are ignored : "{value}" will not be modified.

JSON and missing fields

In a REST API, PATCH update calls may update only certain fields. When using structs with plain types, it is impossible to differentiate between empty fields {"name":""}, null fields : {"name": null} and missing fields : {}.

pointers

type Example struct {
	Name *string `db:"name"`
}

Using pointers, one can differentiate between empty fields and null/missing fields, but not between null and missing fields. In this case, nil values are usually considered missing.

sqlbind will never expand nil pointer values in ::names and ::name=::value.

jsontypes

jsontypes defines types that will be able to manage various cases : null values, missing JSON fields, zero/empty values, read-only values. All types are automatically converted from/to their underlying type when reading/writing to the database.

type Example struct {
	Name jsontypes.NullString `db:"name"`
}

• jsontypes.NullString will either be expanded to "" ("" in JSON), NULL (null in JSON) or not expanded (absent from JSON).
• jsontypes.String will either be expanded to "" ("" or null in JSON) or not expanded (absent from JSON)
• jsontypes.ROString will never be expanded

See jsontypes for all types.

More generally, all structs that implement Missing() bool will be managed by sqlbind.

Result struct binding

type Example struct {
	ID   int    `db:"id,ro"`
	Name string `db:"name"`
}
rows, err := db.Query("SELECT * FROM example")
...
defer rows.Close()
for rows.Next() {
    e := Example{}
    err = sqlbind.Scan(rows, &e)
}

QueryRow does not expose column names, Query+ScanRow can be used instead.

rows, err := db.Query("SELECT * FROM example")
err := sqlbind.ScanRow(rows, &e) // closes

Slices of structs are not mapped, only structs.

Performance

sqlbind uses reflection to parse structs. In order to achieve the best performance, it is recommended to register your structs before binding :

sqlbind.Register(Example{}, Foo{})

Benchmark against sqlx:

BenchmarkSQLBindNamedRegister-4  	 1000000	      2069 ns/op	     288 B/op	       5 allocs/op
BenchmarkSqlxNamed-4             	  500000	      2382 ns/op	     624 B/op	      13 allocs/op

Instances

You can build a SQLBinder instance :

s := sqlbind.New(sqlbind.MySQL)
s.Register(Example{}, Foo{})
s.Named("SELECT * FROM example WHERE name=:name", e)

License

License: MIT - see LICENSE