|go ahead... be a heretic|
Re^3: Help Sorting a CSV Fileby erix (Parson)
|on Oct 07, 2019 at 14:20 UTC||Need Help??|
However, there is a another step in-between text and database, in the form of a "Foreign Data Wrapper", to let the database serve up the underlying (csv-)textfile:
Results are (again):
Such SQL using a 'Foreign Table' reads the underlying csv/text file(s). The annoying part is setting up the table , for instance in the case of tables with hundreds of columns you need a separate little application to do that, and this is where perl comes in handy (reading the header line and turning it into the CREATE TABLE column-list).
Weaknesses and strengths:
Advantages: SQL access to csv data. DBD::CSV delivers SQL as in SQL::Statement::Syntax which is nice but basic. The Data Wrapper's Foreign Table gives you access to the data via the full postgres SQL engine: Window Functions, Grouping Sets/Cube/Rollup, Generated Columns, Partitioning , etc., etc.)
Disadvantages: Needs Postgres, and with extension file_fdw installed. Table remains read-only. No indexing possible, so that huge csv-files can make it slow (alhough 'copying' onto a materialized view  on the foreign table makes of course indexing possible again). Filesystem access for the postgres superuser is necessary.
It all depends what you want to do.
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