cff37b40bd
Because of sqlite's flexible typing, even though the column was declared as jsonb, the values are stored as the TEXT-typed json because they're converted to strings by Value/Scan. If the table is strict with a BLOB column, the example fails because of the type mismatch. This can be fixed by using the `jsonb()` function to convert incoming string-typed json and the `json()` function to convert outgoing binary-typed jsonb. The example is expanded to show both of these approaches. Note that both approaches use the same string-typed marshalling functions because the conversion to jsonb occurs within sqlite3, not within the Go code. SQLite docs state that the binary format is internal and applications shouldn't try to generate it: https://sqlite.org/json1.html#jsonb
130 lines
2.7 KiB
Go
130 lines
2.7 KiB
Go
package main
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import (
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"database/sql"
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"database/sql/driver"
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"encoding/json"
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"fmt"
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_ "github.com/mattn/go-sqlite3"
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"log"
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"os"
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)
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type Tag struct {
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Name string `json:"name"`
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Country string `json:"country"`
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}
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func (t *Tag) Scan(value interface{}) error {
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return json.Unmarshal([]byte(value.(string)), t)
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}
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func (t *Tag) Value() (driver.Value, error) {
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b, err := json.Marshal(t)
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return string(b), err
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}
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func main() {
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os.Remove("./foo.db")
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db, err := sql.Open("sqlite3", "./foo.db")
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if err != nil {
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log.Fatal(err)
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}
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defer db.Close()
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// Using a json-typed column
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// Verify type: `create table foo (tag text) strict`
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_, err = db.Exec(`create table foo (tag json)`)
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if err != nil {
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log.Fatal(err)
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}
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stmt, err := db.Prepare("insert into foo(tag) values(?)")
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if err != nil {
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log.Fatal(err)
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}
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defer stmt.Close()
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_, err = stmt.Exec(`{"name": "mattn", "country": "japan"}`)
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if err != nil {
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log.Fatal(err)
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}
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_, err = stmt.Exec(`{"name": "michael", "country": "usa"}`)
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if err != nil {
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log.Fatal(err)
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}
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var country string
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err = db.QueryRow("select tag->>'country' from foo where tag->>'name' = 'mattn'").Scan(&country)
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if err != nil {
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log.Fatal(err)
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}
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fmt.Println(country)
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var tag Tag
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err = db.QueryRow("select tag from foo where tag->>'name' = 'mattn'").Scan(&tag)
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if err != nil {
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log.Fatal(err)
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}
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fmt.Println(tag.Name)
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tag.Country = "日本"
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_, err = db.Exec(`update foo set tag = ? where tag->>'name' == 'mattn'`, &tag)
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if err != nil {
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log.Fatal(err)
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}
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err = db.QueryRow("select tag->>'country' from foo where tag->>'name' = 'mattn'").Scan(&country)
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if err != nil {
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log.Fatal(err)
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}
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fmt.Println(country)
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// Using a jsonb-typed column
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// Verify type: `create table bar (tag blob) strict`
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_, err = db.Exec(`create table bar (tag jsonb)`)
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if err != nil {
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log.Fatal(err)
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}
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stmt, err = db.Prepare("insert into bar(tag) values(jsonb(?))")
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if err != nil {
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log.Fatal(err)
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}
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defer stmt.Close()
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_, err = stmt.Exec(`{"name": "mattn", "country": "japan"}`)
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if err != nil {
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log.Fatal(err)
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}
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_, err = stmt.Exec(`{"name": "michael", "country": "usa"}`)
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if err != nil {
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log.Fatal(err)
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}
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err = db.QueryRow("select tag->>'country' from bar where tag->>'name' = 'mattn'").Scan(&country)
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if err != nil {
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log.Fatal(err)
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}
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fmt.Println(country)
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err = db.QueryRow("select json(tag) from bar where tag->>'name' = 'mattn'").Scan(&tag)
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if err != nil {
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log.Fatal(err)
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}
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fmt.Println(tag.Name)
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tag.Country = "日本"
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_, err = db.Exec(`update bar set tag = jsonb(?) where tag->>'name' == 'mattn'`, &tag)
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if err != nil {
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log.Fatal(err)
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}
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err = db.QueryRow("select tag->>'country' from bar where tag->>'name' = 'mattn'").Scan(&country)
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if err != nil {
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log.Fatal(err)
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}
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fmt.Println(country)
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}
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