PGX and FieldDescription

[wshekrota]

I may have this wrong but did something change in this type? Doc indicates there is a DataTypeName string?
Name seems to work fine but other fields not found.

d.DataTypeName undefined (type pgconn.FieldDescription has no field or method DataTypeName)

import "github.com/jackc/pgx/v5"
.
.
rows, err := db.Query(context.Background(), sqCmd)
.
.
// rows is the result of having done a select * from table
.
Fds := rows.FieldDescriptions()
var tableFieldNames, tableFieldTypes []string
for _, d := range Fds {
tableFieldNames = append(tableFieldNames, d.Name)
tableFieldTypes = append(tableFieldTypes, d.DataTypeName)
}

I'm trying to assert data types
Thanks for any ideas.
-Walt

[jackc]

I may have this wrong but did something change in this type? Doc indicates there is a DataTypeName string?

I think you are looking at the v3 docs. That doesn't exist in v4 or v5. https://pkg.go.dev/github.com/jackc/pgx/[email protected]/pgconn#FieldDescription.

The protocol doesn't directly expose the type name. Only the OID. You may be able to get the pgtype.Map from your Conn and call https://pkg.go.dev/github.com/jackc/pgx/[email protected]/pgtype#Map.TypeForOID to get the name (assuming pgx/pgtype knows what it is)

[wshekrota]

yeah that goes to v3 what I was looking at .... I see now you do have newer. Google is my friendemy right.
TypeForOid ok I see that will have to see how to get the oid at first glance that looks like a query which is too far to go I think.
Is the OID available in pgx internals?
Thanks

[wshekrota]

Going into the future will FieldDescription name continue to exist as it does now? Can I depend on that or will there be an alternative?
Looks like I see TableOID also...
ok I have a direction thanks.

[wshekrota]

I have the DataTypeOID fine but ...
Looks like I have to go back to PGX v3 before I get a Conn like this...
type Conn struct {
Pid int32 // backend pid
SecretKey int32 // key to use to send a cancel query message to the server
RuntimeParams map[string]string // parameters that have been reported by the server
PgTypes map[Oid]PgType // oids to PgTypes

TxStatus byte
// contains filtered or unexported fields

}
Newer ones say unexported fields in Conn.
Is there any other way I can get this typing to work without a hack :) ?
Thanks.

[jackc]

Everything is still available, but usually now via method instead of an exposed field.

https://pkg.go.dev/github.com/jackc/pgx/v5/pgconn#PgConn.PID
https://pkg.go.dev/github.com/jackc/pgx/v5/pgconn#PgConn.SecretKey
https://pkg.go.dev/github.com/jackc/pgx/v5/pgconn#PgConn.ParameterStatus

...

https://pkg.go.dev/github.com/jackc/pgx/v5#Conn.TypeMap gets you the pgtype.Map. From there you can call TypeForOID. It is only a map lookup. It is not a database query.

[wshekrota]

I got the oid from the field description then cobbled a switch with some known oids then using reflect.TypeOf in default rapidly exposed the small set of asserts. Adding new oids to case sets as I went.Pgtype.numeric Interface{} Are 2 that came up requiring research.I’ll look through the Conn.TypeMap you have suggested to see if it works better.Thanks for your time in this I have a working postgres to document db converter. Well almost.WaltSent from my iPadOn Sep 11, 2023, at 11:00 AM, Jack Christensen ***@***.***> wrote: Everything is still available, but usually now via method instead of an exposed field. https://pkg.go.dev/github.com/jackc/pgx/v5/pgconn#PgConn.PID https://pkg.go.dev/github.com/jackc/pgx/v5/pgconn#PgConn.SecretKey https://pkg.go.dev/github.com/jackc/pgx/v5/pgconn#PgConn.ParameterStatus ... https://pkg.go.dev/github.com/jackc/pgx/v5#Conn.TypeMap gets you the pgtype.Map. From there you can call TypeForOID. It is only a map lookup. It is not a database query. —Reply to this email directly, view it on GitHub, or unsubscribe.You are receiving this because you authored the thread.Message ID: ***@***.***>

[wshekrota]

Looks like the TypeMap codec method PreferredFormat() returns bool not the int16 format code. I get 1 and 0. Is that even the right method?To convert the column values generated by the next to go values I need to…PlanScan()ThenDecodeValue()?What is the format parameter and how do I provide it?ThanksWaltSent from my iPadOn Sep 11, 2023, at 11:00 AM, Jack Christensen ***@***.***> wrote: Everything is still available, but usually now via method instead of an exposed field. https://pkg.go.dev/github.com/jackc/pgx/v5/pgconn#PgConn.PID https://pkg.go.dev/github.com/jackc/pgx/v5/pgconn#PgConn.SecretKey https://pkg.go.dev/github.com/jackc/pgx/v5/pgconn#PgConn.ParameterStatus ... https://pkg.go.dev/github.com/jackc/pgx/v5#Conn.TypeMap gets you the pgtype.Map. From there you can call TypeForOID. It is only a map lookup. It is not a database query. —Reply to this email directly, view it on GitHub, or unsubscribe.You are receiving this because you authored the thread.Message ID: ***@***.***>

[jackc]

Looks like the TypeMap codec method PreferredFormat() returns bool not the int16 format code.

https://pkg.go.dev/github.com/jackc/pgx/[email protected]/pgtype#Map.FormatCodeForOID and all the implementers of PreferredFormat return int16 not bool...

I get 1 and 0.

1 and 0 are the underlying values for the binary and text format respectively.

---

To convert the column values generated by the next to go values I need to…PlanScan()ThenDecodeValue()?

Something like that is possible... but unless you are doing something very unusual you shouldn't need to be working at that low level. You could call Rows.Values() to have pgx convert and return all values in the row.