Use memfs for PostgreSQL

[moltar]

By setting this:

PG_DATA: /dev/shm/pgdata/data

We could use memfs, and then speed up the container.

Other options and ideas for the test speed-ups:

• https://marcopeg.com/how-to-run-postgres-for-testing-in-docker/
• https://gajus.com/blog/setting-up-postgre-sql-for-running-integration-tests

I've been running tests for years with these options, without any known side effects:

-c shared_buffers=128MB -c fsync=off -c synchronous_commit=off -c full_page_writes=off

[cristianrgreco]

Hi @moltar. Interesting, thanks for the info.

Feel free to raise a PR and if tests pass I don't see any issue in merging.

[moltar]

Should this be a `withX` helper method you think?

[cristianrgreco]

@moltar Sure

[digital88]

This already is possible using latest TC API:

import { Client } from "pg";
import { PostgreSqlContainer } from "..";

describe("PostgreSql InMemory DB example", { timeout: 180_000 }, () => {
  it("should run as in-memory db", async () => {
    // TmpFs mount is supported only if your HOST system is linux.
    const container = await new PostgreSqlContainer("postgres:17-alpine")
      .withTmpFs({
        "/var/lib/postgresql/data": "rw,size=256m",
      })
      .withSharedMemorySize(256 * 1024 * 1024) // Default shmem size = 64mb.
      .withEnvironment({ PGDATA: "/var/lib/postgresql/data/pgdata" })
      .withUsername("myUser")
      .withPassword("t0pSecret")
      .withDatabase("test_db")
      .withCommand([
        "postgres",
        "-c",
        "shared_buffers=256MB",
        "-c",
        "fsync=off",
        "-c",
        "synchronous_commit=off",
        "-c",
        "full_page_writes=off",
      ])
      .start();
    // Read more here:
    // https://www.postgresql.org/docs/current/runtime-config-resource.html
    // https://www.postgresql.org/docs/current/runtime-config-wal.html

    const client = new Client({
      connectionString: container.getConnectionUri(),
    });
    await client.connect();

    let q = await client.query("SELECT setting,unit FROM pg_settings where name='shared_buffers'");
    const setting = q.rows[0]["setting"];
    const unit = q.rows[0]["unit"];
    expect(setting).toBe("32768");
    expect(unit).toBe("8kB");
    // 32768 * 8kb = 262144kB = 256MB

    q = await client.query(
      "SELECT setting,unit FROM pg_settings where name='fsync' or name='synchronous_commit' or name='full_page_writes'"
    );
    q.rows.forEach((row) => {
      const setting = row["setting"];
      expect(setting).toBe("off");
    });

    await client.end();
    await container.stop();
  });
});

Database snapshots feature was implemented in v10.23.0