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Version: 2.8.x(Latest)

ORM supports passing custom context variables for asynchronous IO control, context information transmission (especially transmission of trace information), and nested transaction support.

We can pass custom context variables to an ORM object using the Ctx method. The Ctx method is essentially a chainable operation, and the context passed in is only effective for the current DB interface object. The method is defined as follows:

func Ctx(ctx context.Context) DB

Request Timeout Control​

Let's look at an example of controlling the request timeout duration using context variables.

ctx, cancel := context.WithTimeout(context.Background(), time.Second)
defer cancel()
_, err := db.Ctx(ctx).Query("SELECT SLEEP(10)")
fmt.Println(err)

In this example, executing sleep 10 seconds will inevitably cause a timeout. After execution, the output is:

context deadline exceeded, SELECT SLEEP(10)

Trace Information​

Context variables can also pass trace information, and when combined with the logging component, can print trace information to logs (only when ORM logging is enabled). Please refer to the trace topic chapter: Service Tracing.

Model Context Operations​

Model objects also support context variable passing, using the Ctx method as well. Let's look at a simple example by modifying the example from the second section using model operations.

package main

import (
    "github.com/gogf/gf/v2/frame/g"
    "github.com/gogf/gf/v2/os/gctx"
)

func main() {
    _, err := g.DB().Model("user").Ctx(gctx.New()).All()
    if err != nil {
        panic(err)
    }
}

After execution, the terminal output is:

2020-12-28 23:46:56.349 [DEBU] {38d45cbf2743db16f1062074f7473e5c} [  5 ms] [default] [rows:0  ] SHOW FULL COLUMNS FROM `user`
2020-12-28 23:46:56.354 [DEBU] {38d45cbf2743db16f1062074f7473e5c} [  5 ms] [default] [rows:100] SELECT * FROM `user`
tip

The SHOW FULL COLUMNS FROM user`` query is used by the ORM component to fetch data table fields, which queries each table only once before execution and caches the results in memory.

Nested Transaction Support​

Support for nested transactions relies on hierarchical passing of Context variables. For details, please refer to the chapter: ORM - Transaction.