Re: Loading 500m json files to database - Mailing list pgsql-general

On Mar 23, 2020, at 7:11 PM, David G. Johnston <david.g.johnston@gmail.com> wrote:

On Mon, Mar 23, 2020 at 3:24 AM pinker <pinker@onet.eu> wrote:

time for i in datafiles/*; do
  psql -c "\copy json_parts(json_data) FROM $i"&
done

Don't know whether this is faster but it does avoid spinning up a connection multiple times.

#bash, linux

    function append_each_split_file_to_etl_load_script() {
        for filetoload in ./*; do
            ronumber="$(basename $filetoload)"
            # only process files since subdirs can be present
            if [[ -f "$filetoload" ]]; then
                echo ""
                echo "\set invoice"' `cat '"'""$filetoload""'"'`'
                echo ", ('$ronumber',:'invoice')"
            fi >> "$PSQLSCRIPT"
        done

        echo ""  >> "$PSQLSCRIPT"
        echo ";" >> "$PSQLSCRIPT"
        echo ""  >> "$PSQLSCRIPT"
    }

There is a bit other related code that is needed (for my specific usage) but this is the core of it.  Use psql variables to capture the contents of each file into a variable and then just perform a normal insert (specifically, a VALUES (...), (...) variant).  Since you can intermix psql and SQL you basically output a bloody long script, that has memory issues at scale - but you can divide and conquer - and then "psql --file bloody_long_script_part_1_of_100000.psql".

David J.