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Silent switching from binary to text copy

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#358 6 comments 1 reaction 0 assignees View on GitHub

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Assessment

Difficulty
3/5
Estimated time
1-2 days
Newbie friendliness
48/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Stale
Tech stack
cpp, postgresql
Domain
database

Research direction

Start by tracing the pg_use_binary_copy setting and the COPY format selection used when inserting into PostgreSQL. Reproduce the NUMERIC and FLOAT cases from the issue with pg_debug_show_queries enabled, then verify that the NUMERIC case follows the intended binary-copy behavior without regressing the existing FLOAT case.

Written by the indexing model from the issue text.

Description

What happens?

Despite having set pg_use_binary_copy=true, if the target table has a column with NUMERIC type then text format is used (instead of binary) when copying data from DuckDB to PostgreSQL.

To Reproduce

  1. Configure duckdb-postgres as follows:

    • SET pg_debug_show_queries=true;
    • SET pg_use_binary_copy=true;

  2. Create a DuckDB table: CREATE OR REPLACE TABLE mytable (id INTEGER, value NUMERIC);.

  3. Insert a row into the table created at step 2: INSERT INTO mytable VALUES (1, 1.234);.

  4. Open a connection to PostgreSQL: ATTACH 'dbname=<dbname> user=<user> password=<password> host=<host>' AS pg (TYPE postgres);.

  5. Create a PostgresSQL table:

    CALL postgres_execute('pg', '
    DROP TABLE IF EXISTS mytable;
    CREATE TABLE mytable (
        id INTEGER,
        value NUMERIC
    );'
);

  6. Copy data from DuckDB to PostgreSQL: INSERT INTO pg.mytable (id, value) SELECT id, value FROM mytable;. The following line would show up in debug messages: COPY "public"."mytable" FROM STDIN (FORMAT TEXT, NULL ').

  7. Repeat step 5 by replacing NUMERIC with FLOAT.

  8. Repeat step 6. Now, data would be copied using the binary format (debug message: COPY "public"."mytable" ("id", "value") FROM STDIN (FORMAT BINARY)).

OS:

Debian 12

PostgreSQL Version:

17.5

DuckDB Version:

v1.4.0-dev2508

DuckDB Client:

Python

Full Name:

Alessandro Cerioni

Affiliation:

État de Genève

Have you tried this on the latest main branch?
  • I agree
Have you tried the steps to reproduce? Do they include all relevant data and configuration? Does the issue you report still appear there?
  • I agree
Dominant language
C++
Stars
375
Forks
113
Avg merge
6h 42m
Merged PRs (30d)
30

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