Retrieving multiple datastore entities of the same kind in a transaction - go

I need to retrieve a list of items of one Kind where the key is the name of the entity.
Based on each item in the returned list I need to retrieve a list of items from another kind where the key is the name.
I think I need to run this in a transaction and I cannot find how to get multiple entities within a transaction without prior knowledge of a list of keys(GetMulti()). The code I am currently using follows with error handling removed for brevity.
Appreciate any assistance you can offer.
q := datastore.NewQuery("Plans").Namespace(TargetNamespace).
Filter("Status =", PlanActive)
_, err := ps.DSClient.GetAll(tctx, q, &sponsorPlans)
if err != nil {
return
}
for spIndex, spItem := range sponsorPlans {
updateMembers := false
// for each sponsor plan get all the related active client plans
q := datastore.NewQuery("ClientPlans").Namespace(hasu.TheConstants.Namespace).
Filter("Name =", sponsorPlans[spIndex].Name)
memberPlanKeys, err := ps.DSClient.GetAll(tctx, q, &memberPlans)
if err != nil {
return
}
for index := range memberPlans {
memberPlans[index].CapSpend = 0
memberPlans[index].RenewalDate = sponsorPlans[spIndex].RenewalDate
memberPlans[index].MemberCap = spItem.MemberCap
memberPlans[index].Services = spItem.Services
memberPlans[index].Status = spItem.Status
memberPlans[index].TotalLiveSessions = spItem.TotalLiveSessions
}
_, err = ps.DSClient.PutMulti(tctx, memberPlanKeys, memberPlans)
if err != nil {
return
}
}

Related

Golang query scan not scanning query correctly into struct

I am having trouble with scanning from a pgx query in Golang. The id field is always that of the last record. If I un-comment the var person Person declaration at the top of the function, every id is 3. There are 3 records with id's from 1 to 3 in my db. When I comment that declaration and declare the variable in the rows.Next() loop I get the correct id's. I can't figure out why the personId isn't being correctly overwritten
output from marshalled JSON with the var declared at the top of the function.
[{"person_id":3,"first_name":"Mark","last_name":"Brown"},{"person_id":3,"first_name":"Sam","last_name":"Smith"},{"person_id":3,"first_name":"Bob","last_name":"Jones"}]
output after declaring person every iteration of the scan loop
[{"person_id":1,"first_name":"Mark","last_name":"Brown"},{"person_id":2,"first_name":"Sam","last_name":"Smith"},{"person_id":3,"first_name":"Bob","last_name":"Jones"}]
I have this struct
// Person model
type Person struct {
PersonId *int64 `json:"person_id"`
FirstName *string `json:"first_name"`
LastName *string `json:"last_name"`
}
Here is my query function
func getPersons(rs *appResource, companyId int64) ([]Person, error) {
// var person Person
var persons []Person
queryString := `SELECT
user_id,
first_name,
last_name,
FROM users
WHERE company_id = $1`
rows, err := rs.db.Query(context.Background(), queryString, companyId)
if err != nil {
return persons, err
}
for rows.Next() {
var person Person
err = rows.Scan(
&person.PersonId,
&person.FirstName,
&person.LastName)
if err != nil {
return persons, err
}
log.Println(*person.PersonId) // 1, 2, 3 for both var patterns
persons = append(persons, person)
}
if rows.Err() != nil {
return persons, rows.Err()
}
return persons, err
}
I believe that you have discovered a bug (or, at least, unexpected behaviour) in github.com/jackc/pgx/v4. When running Scan it appears that if the pointer (so person.PersonId) is not nil then whatever it is pointing to is being reused. To prove this I replicated the issue and confirmed that you can also fix it with:
persons = append(persons, person)
person.PersonId = nil
I can duplicate the issue with this simplified code:
conn, err := pgx.Connect(context.Background(), "postgresql://user:password#127.0.0.1:5432/schema?sslmode=disable")
if err != nil {
panic(err)
}
defer conn.Close(context.Background())
queryString := `SELECT num::int FROM generate_series(1, 3) num`
var scanDst *int64
var slc []*int64
rows, err := conn.Query(context.Background(), queryString)
if err != nil {
panic(err)
}
for rows.Next() {
err = rows.Scan(&scanDst)
if err != nil {
panic(err)
}
slc = append(slc, scanDst)
// scanDst = nil
}
if rows.Err() != nil {
panic(err)
}
for _, i := range slc {
fmt.Printf("%v %d\n", i, *i)
}
The output from this is:
0xc00009f168 3
0xc00009f168 3
0xc00009f168 3
You will note that the pointer is the same in each case. I have done some further testing:
Uncommenting scanDst = nil in the above fixes the issue.
When using database/sql (with the "github.com/jackc/pgx/stdlib" driver) the code works as expected.
If PersonId is *string (and query uses num::text) it works as expected.
The issue appears to boil down to the following in convert.go:
if v := reflect.ValueOf(dst); v.Kind() == reflect.Ptr {
el := v.Elem()
switch el.Kind() {
// if dst is a pointer to pointer, strip the pointer and try again
case reflect.Ptr:
if el.IsNil() {
// allocate destination
el.Set(reflect.New(el.Type().Elem()))
}
return int64AssignTo(srcVal, srcStatus, el.Interface())
So this handles the case where the destination is a pointer (for some datatypes). The code checks if it is nil and, if so, creates a new instance of the relevant type as a destination. If it's not nil it just reuses the pointer. Note: I've not used reflect for a while so there may be issues with my interpretation.
As the behaviour differs from database/sql and is likely to cause confusion I believe it's probably a bug (I guess it could be an attempt to reduce allocations). I have had a quick look at the issues and could not find anything reported (will have a more detailed look later).

Is there an API to retrieve the neo4j relationship details using the Go bolt driver?

Using the neo4j Go bolt driver, I am able to get nodes, but not relationships from the graph db.
The Run() API in neo4j.transaction return type is Result which can give nodes, but not to the relationships?
If I try the query in the neo4j browser, it shows me the properties of the relationships, but if I send the same query programmatically, I don’t get anything. Am I missing something?
MATCH (:a {name: ‘foo’})-[r:bar]->() RETURN properties(r)
The above query works
{
"X":"20",
"Y":"40"
}
But the same query sent via the driver returns no error, but has nothing in it.
There might be something wrong with your mapping code.
It should look like this:
func readCoordinates(driver neo4j.Driver) ([]Coordinates, error) {
session := driver.NewSession(neo4j.SessionConfig{})
defer session.Close()
result, err := session.ReadTransaction(executeReadCoordinates)
if err != nil {
return nil, err
}
return result.([]Coordinates), nil
}
func executeReadCoordinates(tx neo4j.Transaction) (interface{}, error) {
records, err := tx.Run("MATCH (:A {name: 'foo'})-[r:BAR]->() RETURN properties(r)", map[string]interface{}{})
if err != nil {
return nil, err
}
var results []Coordinates
for records.Next() {
record := records.Record()
if props, found := record.Get("properties(r)"); !found {
return nil, fmt.Errorf("expected properties not found")
} else {
properties := props.(map[string]interface{})
coordinates := Coordinates{
X: properties["x"].(int64),
Y: properties["y"].(int64),
}
results = append(results, coordinates)
}
}
return results, nil
}
I changed the case of the node label (convention: PascalCase), relationship type (convention: SCREAMING_SNAKE_CASE) and properties (convention: snake_case).
The code assumes those properties are of type int64 and fetches a list.
If you want a single pair of coordinates, then remove the for loop and use records.Single() instead.

How write effective save and update function in beego?

I have the following function in the BaseModel that I can use anywhere.
func (d *Dummy) Save() (int64, error) {
o := orm.NewOrm()
var err error
var count int64
if d.Id == 0 {
count, err = o.Insert(d)
} else {
count, err = o.Update(d)
}
return count, err
}
I am using like this
d := models.Dummy{Id: 10}
d.SomeValue = "x"
d.Save()
The problem is I have "d.OtherValue" is already in DB with value.
After executing this function it's getting updated to 0.
As it is a common model function effective for all models, How can I solve this? Basically, I wanted to do this in a single query just like update/Save Django ORM
You need to load the record first. You are missing the Read(&struct) ORM method:
o := orm.NewOrm()
d := models.Dummy{Id: 10}
readErr:= o.Read(&d)
// check if the record with Id of 10 exists and update...
if readErr!= o.ErrNoRows {
if rowsAffected, err := o.Update(&d); err == nil {
// record updated (rowsAffected indicates the number of affected rows)
}
} else {
// record does not exist, create a new one
id, insertErr:= o.Insert(&d)
if insertErr== nil {
// success
}
}
Then you should check if a record is found by the ORM
For more details you can refer to the Read and Update methods.

Mapping Gorm queries to lists of structs

Go here, using gorm to help me with database stuff.
I have the following function which is working for me:
func (d DbPersister) FetchOrderById(orderId string) (Order,error) {
order := &Order{}
if err := d.GormDB.Table("orders").
Select(`orders`.`order_id`,
`orders`.`quantity`,
`addresses`.`line_1`,
`addresses`.`state`,
`addresses`.`zip`).
Joins("join addresses on addresses.address_id = orders._address_id").
Where("orders.order_id = ?", orderId).
First(order).Error; err != nil {
return Order{}, err
}
return *order,nil
}
So, you give it an orderId, and it fetches that from the DB and maps it to an Order instance.
I now want to look up all a particular user's orders:
func (d DbPersister) FetchAllOrdersByCustomerId(userId string) ([]Order,error) {
orders := []&Order{}
if err := d.GormDB.Table("orders").
Select(`orders`.`order_id`,
`orders`.`quantity`,
`orders`.`status`,
`addresses`.`line_1`,
`addresses`.`state`,
`addresses`.`zip`).
Joins("join addresses on addresses.address_id = orders.shipping_address_id").
Joins("join users on users.user_id = orders.user_id").
Where("users.user_id = ?", userId).
First(orders).Error; err != nil {
return []Order{}, err
}
return orders,nil
}
However, I'm getting compiler errors. I don't believe First(orders) is the correct function to be calling here. Basically do a join between orders and users and give me all of a particular user's orders, which should be a list of Order instances. Can anyone spot where I'm going awry?
Firstly orders := []&Order{} should be orders := make([]Order,0)
Then use Find() instead of First() to get multiple values.
For structs, slices, maps, and other composite types, if no data is contained you can return nil
So your code should be
func (d DbPersister) FetchAllOrdersByCustomerId(userId string) ([]Order,error) {
orders := make([]Order,0)
if err := d.GormDB.Table("orders").
Select(`orders`.`order_id`,
`orders`.`quantity`,
`orders`.`status`,
`addresses`.`line_1`,
`addresses`.`state`,
`addresses`.`zip`).
Joins("join addresses on addresses.address_id = orders.shipping_address_id").
Joins("join users on users.user_id = orders.user_id").
Where("users.user_id = ?", userId).
Find(&orders).Error; err != nil {
return nil, err
}
return orders,nil
}

Getting world state by value

I'm new to blockchain and working with hyperledger fabric (v:0.6 for now) to create an application for learning perspective.
I'm keeping a ledger of financial transactions on blockchain, soon as a transaction takes place (A web based component notifies on transaction occurrence and calls the chaincode).
The structure of transactions looks something like this:
type Transactions struct {
ReferenceNumber string `json:"ReferenceNumber"`
BillNumber string `json:"BillNumber"`
BillingCompany string `json:"BillingCompany"`
Amount string `json:"Amount"`
Status string `json:"Status"`
}
I json marshal this and save it to state with ReferenceNumber as the key.
Now I can get the transaction from state on the basis of ReferenceNumber. But what if I want to get the transaction from state on the basis of let's say 'Status' like how many transactions on the ledger have status as 'reconciled'.
Is there any way to query state not on the basis of key but value?
Worldstate level storage works at the {key,value} level. And as obvious its only intended for a single value lookup for a specified key. I think what you are looking for calls for a next level higher level of Abstraction of WorldState - called Table constructs.
fabric/examples/chaincode/go/asset_management_interactive/asset_management.go has an example on how to create a table with the columns you want. While defining the primary keys of your data structure to hold the transaction, you include Status as one of the keys and you would be able to retrieve data on the basis of Status as well.
Some sample code to create the table is as below
func createTableTwo(stub shim.ChaincodeStubInterface) error {
var columnDefsTableTwo []*shim.ColumnDefinition
columnOneTableTwoDef := shim.ColumnDefinition{Name: "colOneTableTwo",
Type: shim.ColumnDefinition_STRING, Key: true}
columnTwoTableTwoDef := shim.ColumnDefinition{Name: "colTwoTableTwo",
Type: shim.ColumnDefinition_INT32, Key: false}
columnThreeTableTwoDef := shim.ColumnDefinition{Name: "colThreeTableThree",
Type: shim.ColumnDefinition_INT32, Key: true}
columnFourTableTwoDef := shim.ColumnDefinition{Name: "colFourTableFour",
Type: shim.ColumnDefinition_STRING, Key: true}
columnDefsTableTwo = append(columnDefsTableTwo, &columnOneTableTwoDef)
columnDefsTableTwo = append(columnDefsTableTwo, &columnTwoTableTwoDef)
columnDefsTableTwo = append(columnDefsTableTwo, &columnThreeTableTwoDef)
columnDefsTableTwo = append(columnDefsTableTwo, &columnFourTableTwoDef)
return stub.CreateTable("tableTwo", columnDefsTableTwo)
}
Now to insert data into this table, as shown
if len(args) < 4 {
return nil, errors.New("insertRowTableTwo failed. Must include 4 column values")
}
col1Val := args[0]
col2Int, err := strconv.ParseInt(args[1], 10, 32)
if err != nil {
return nil, errors.New("insertRowTableTwo failed. arg[1] must be convertable to int32")
}
col2Val := int32(col2Int)
col3Int, err := strconv.ParseInt(args[2], 10, 32)
if err != nil {
return nil, errors.New("insertRowTableTwo failed. arg[2] must be convertable to int32")
}
col3Val := int32(col3Int)
col4Val := args[3]
var columns []*shim.Column
col1 := shim.Column{Value: &shim.Column_String_{String_: col1Val}}
col2 := shim.Column{Value: &shim.Column_Int32{Int32: col2Val}}
col3 := shim.Column{Value: &shim.Column_Int32{Int32: col3Val}}
col4 := shim.Column{Value: &shim.Column_String_{String_: col4Val}}
columns = append(columns, &col1)
columns = append(columns, &col2)
columns = append(columns, &col3)
columns = append(columns, &col4)
row := shim.Row{Columns: columns}
ok, err := stub.InsertRow("tableTwo", row)
if err != nil {
return nil, fmt.Errorf("insertRowTableTwo operation failed. %s", err)
}
if !ok {
return nil, errors.New("insertRowTableTwo operation failed. Row with given key already exists")
}
Now to query this data by not specifying all the keys, do as below
if len(args) < 1 {
return nil, errors.New("getRowsTableTwo failed. Must include at least key values")
}
var columns []shim.Column
col1Val := args[0]
col1 := shim.Column{Value: &shim.Column_String_{String_: col1Val}}
columns = append(columns, col1)
if len(args) > 1 {
col2Int, err := strconv.ParseInt(args[1], 10, 32)
if err != nil {
return nil, errors.New("getRowsTableTwo failed. arg[1] must be convertable to int32")
}
col2Val := int32(col2Int)
col2 := shim.Column{Value: &shim.Column_Int32{Int32: col2Val}}
columns = append(columns, col2)
}
rowChannel, err := stub.GetRows("tableTwo", columns)
if err != nil {
return nil, fmt.Errorf("getRowsTableTwo operation failed. %s", err)
}
var rows []shim.Row
for {
select {
case row, ok := <-rowChannel:
if !ok {
rowChannel = nil
} else {
rows = append(rows, row)
}
}
if rowChannel == nil {
break
}
}
jsonRows, err := json.Marshal(rows)
if err != nil {
return nil, fmt.Errorf("getRowsTableTwo operation failed. Error marshaling JSON: %s", err)
}
return jsonRows, nil
Once you have inserted the data, the API stub.GetRows("tableTwo", columns) lets you retrieve it without specifying all the key columns.
Above code is quoted from a file which was present in the Fabric github repo earlier in the following path gerrit/src/github.com/hyperledger/fabric/bddtests/chaincode/go/table/table.go
Hope this helps.
In Hyperledger Fabric v1.0 you can model your data as JSON and utilize CouchDB as the state database. In this case you can directly query on any field of the JSON.
There is an example of such data patterns in the marbles02 chaincode.
There are various other ledger and state database options in v1.0.

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