Comments (5)
How deal with this?
This function can return the Value of the field
// get the value of unexported struct
func getUnexportedHDBStruct(field interface{}) reflect.Value {
rs := reflect.Indirect(reflect.ValueOf(field))
return rs.Field(8)
}
The index 8 is the value and you need to specify return the []byte
v := getUnexportedHDBStruct(field)
fmt.Print(v.Bytes())
from go-hdb.
Please double check on
https://github.com/SAP/go-hdb/blob/master/driver/lobexample_test.go
as explanation how to deal with LOB types. In essence the Go lob type needs to provide a Reader resp a Writer interface for good reasons. LOB is 'large objects' which shouldn't necessarily be allocated as strings or bytes. If needed a strings or bytes Buffer can be used for conversion to string and / or byte[].
from go-hdb.
Ok, but I have a problem getting the value of the BLOB column.
Look this example of how I manage the decimal and blob types. Is you ExampleLob_read but for many columns.
db, err := sql.Open("hdb", connstring)
if err != nil {
log.Fatal(err)
}
defer db.Close()
query := "select decimal_column, blob_column from test"
rows, err := db.Query(query)
if err != nil {
log.Fatal(err)
}
defer rows.Close()
//The 2 is the total columns returned in query
recordPointers := make([]interface{}, 2)
//For Decimal Column
var t driver.Decimal
recordPointers[0] = &t
//For BLOB Column
b := new(bytes.Buffer)
var lob driver.Lob
lob.SetWriter(b)
recordPointers[1] = &lob
for rows.Next() {
// Scan the result into the column pointers...
if err := rows.Scan(recordPointers...); err != nil {
log.Fatal(err)
}
for _, v := range recordPointers {
switch x := v.(type) {
case *driver.Lob:
//How deal with this? I need the value
case *driver.Decimal:
d := (*big.Rat)(x)
log.Print(d.FloatString(6))
default:
log.Print("is not BLOB or Decimal")
}
}
}
from go-hdb.
Scan is going to take care, that the data of the BLOB is written to the bytes.Buffer. To access the data any method of bytes.Buffer can be used, e.g. b.Bytes(), b.String()...
Please be aware that the driver is not going to clear (refresh) the buffer implicitly, so in the example each iteration (rows.Next()) is going to append the BLOB record data to buffer b.
from go-hdb.
Tested and works. Thanks for help.
Code for documentation:
db, err := sql.Open("hdb", connstring)
if err != nil {
log.Fatal(err)
}
defer db.Close()
query := "select decimal_column, blob_column from test"
rows, err := db.Query(query)
if err != nil {
log.Fatal(err)
}
defer rows.Close()
//The 2 is the total columns returned in query
recordPointers := make([]interface{}, 2)
//For Decimal Column
var t driver.Decimal
recordPointers[0] = &t
//For BLOB Column
b := new(bytes.Buffer)
var lob driver.NullLob
lob.Lob = new(driver.Lob)
lob.Lob.SetWriter(b)
recordPointers[1] = &lob
for rows.Next() {
// Scan the result into the column pointers...
if err := rows.Scan(recordPointers...); err != nil {
log.Fatal(err)
}
for _, v := range recordPointers {
switch x := v.(type) {
case *driver.NullLob:
if x.Valid {
log.Print(b.Bytes())
} else {
log.Print("NULL")
}
b.Reset()
case *driver.Decimal:
d := (*big.Rat)(x)
log.Print(d.FloatString(6))
default:
log.Print("is not BLOB or Decimal")
}
}
}
from go-hdb.
Related Issues (20)
- [Feature Request] Distribution settings hardcoded to OFF? HOT 8
- comments at the beginning of the query throws error HOT 9
- Bug - wrong scan type for decimal with null values HOT 6
- protocol error: invalid number of lob parameter ids 1 HOT 4
- [defect] insert lob with size more or equal to 8192 will fail HOT 1
- rows.Next does not stream all rows HOT 2
- Unable to open database connection due to DSN parsing error HOT 1
- dial tcp: missing address HOT 1
- goroutine leak detected in the driver package: callConverter HOT 1
- goroutine leak in driver package: init() HOT 2
- Does go-hdb support IP as the 'endpoint' of hana cloud connection? HOT 3
- Connection via hdbuserstore key does not work? HOT 1
- Connecting to Hana Cloud instance from local system gives connection error HOT 1
- Switch go.mod version to Go 1.21.0 HOT 2
- Consider going back to `go 1.21` in go.mod directive HOT 2
- Why adding options to flag in an embedded library? HOT 1
- ld: symbol(s) not found for architecture arm64 HOT 1
- Example code result error
- Support for `databaseName` query param HOT 1
- EOF error when using x509 certificate for login on HANA Cloud HOT 11
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from go-hdb.