Multidimensional array flattened when using CopyFrom instead of Exec+Insert
Author: rrb3942Created Sep 16, 2025Updated Jul 1, 2026
Labelsbug
Describe the bug When using CopyFrom to insert a string value of a postgres formatted multidimensional array, the array is getting flattened. If inserted via Exec the dimensions are properly persevered.
My specific scenario is bulk loading from a csv with fields containing postgres formatted arrays into a text[][] column.
To Reproduce Steps to reproduce the behavior:
In postgres:
create table array_test ( array_col text[][] );package main
import (
"context"
"fmt"
"os"
"github.com/jackc/pgx/v5"
)
func main() {
conn, err := pgx.Connect(context.Background(), os.Getenv("DATABASE_URL"))
if err != nil {
fmt.Fprintf(os.Stderr, "Unable to connect to database: %v\n", err)
os.Exit(1)
}
defer conn.Close(context.Background())
multi := "{{one,two,three},{four,five,six}}"
rows := [][]any{
{multi},
}
//will insert as {{one,two,three},{four,five,six}}
_, err = conn.Exec(context.Background(), "insert into array_test (array_col) values ($1)", multi)
if err != nil {
fmt.Println(err)
os.Exit(1)
}
//will insert as {one,two,three,four,five,six}
_, err = conn.CopyFrom(context.Background(), pgx.Identifier{"array_test"}, []string{"array_col"}, pgx.CopyFromRows(rows))
if err != nil {
fmt.Println(err)
os.Exit(1)
}
fmt.Println("insert ok")
}Expected behavior Array dimensions to be preserved and identical behavior to Exec+Insert.
Actual behavior Array dimensions flattened.
Version
- Go: create table array_test ( array_col text[][] );
- PostgreSQL: PostgreSQL 17.6 (Debian 17.6-1.pgdg12+1) on x86_64-pc-linux-gnu, compiled by gcc (Debian 12.2.0-14+deb12u1) 12.2.0, 64-bit
- pgx: v5.7.6
Additional context psql with COPY or \COPY from the csv works as expected.
Source: jackc/pgx