An alternative is just to use a 'bytea' or a bitstring in Postgres since you have a hash value anyhow.
* It'll take 9 bytes rather than 8. But space is usually cheap nowadays. * a bitstring will take exactly 8 bytes. * a bytea is varying and can be extended to a larger hash later easily if needed. * You can get a hex representation directly in the psql(1) console. * The data becomes more agnostic: you don't need to know the int->uint translation is needed and other systems will have an easier time interoperating. * You won't accidentally do integer arithmetic on the hash value. Of course, the overhead should be measured, but I don't think it'll be that big in practice. The major drawback is when doing table scanning where more bytes are stuffed in there. If the system isn't efficiency-critical I'd strongly recommend storing data in a representation which match the actual data you are working with. On Sun, Jul 30, 2017 at 4:27 AM Andy Balholm <andybalh...@gmail.com> wrote: > var i uint64 > var j int64 > … > j = int64(i) > > This performs the same conversion that C would do automatically when > assigning i to j, but Go requires you to be a little more explicit. > > On Jul 29, 2017, at 6:54 PM, Tong Sun <suntong...@gmail.com> wrote: > > Neither PostgreSQL[1] nor SQLite[2] support unsigned 64-bit integers at > the SQL level. > However, I do need to save those unsigned 64-bit integers as-is into > database, as they are not numbers but hash values. > > What's the proper way to cast my uint64 as database *signed* integer and > back safely in Go? > > Let's use 8-bit variable as example, in C, I just *assign* > the unsigned 8-bit variable to a signed 8-bit variable, so 255 will "*looks > like*" -1 when in latter form. However, *no info is lost*, and when I > assign it back from signed 8-bit variable, I'm still getting 255. How to > do the same thing in Go? > > Thanks > > [1] > https://stackoverflow.com/questions/21909027/postgres-data-types-how-to-store-uint64-in-postresql > [2] https://sqlite.org/datatype3.html > > > -- > You received this message because you are subscribed to the Google Groups > "golang-nuts" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to golang-nuts+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. > > > -- > You received this message because you are subscribed to the Google Groups > "golang-nuts" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to golang-nuts+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
