#Hosi121/postgres_session

Native adapter for moonbit-community/postgres@0.0.8, reusing its async protocol client and pgpool. There is no libpq dependency, foreign worker or extra pool. Tested with PostgreSQL 17 and the repository's pinned MoonBit toolchain.

#Install and use

Apache-2.0. After registry publication: moon add Hosi121/postgres_session. Your moon.mod imports:

import {
  "Hosi121/sql_session@0.1.0",
  "Hosi121/postgres_session@0.1.0",
  "moonbit-community/postgres@0.0.8",
  "moonbitlang/async@0.22.1",
}

Import "Hosi121/postgres_session" @postgres, "moonbit-community/postgres/client" @client, and "moonbit-community/postgres/pgpool" @pgpool in the consumer package. Inside an async function:

let config = @pgpool.Config::new(
  "127.0.0.1", user="app", password="password", dbname="app",
  ssl_mode=@client.SslMode::Disable, // local test only; default is VerifyFull
  application_name="example",
  pool=@pgpool.PoolConfig::new(4, recycling_method=@pgpool.RecyclingMethod::clean()),
)
@postgres.with_database(config, async fn(db) {
  let rows = db.with_transaction(@pgpool.TransactionOptions::new(), async fn(tx) {
    tx.query("INSERT INTO notes(body) VALUES ($1) RETURNING id", params=["hello"])
  })
  let id : Int = rows[0].get("id")
  println(id)
})

Use an Int64 decode for a BIGINT column. with_database owns the background task group, database and leases. Applications already owning a TaskGroup[Unit] can call database(config, group) instead; the group must outlive every scope and close_and_wait().

#Types and behavior

The returned type is @sql.Database[&@client.ToSql, Row, @client.QuerySummary, @pgpool.TransactionOptions]. Trait-object parameters use upstream typed ToSql implementations, with checked PostgreSQL type acceptance; they are not unchecked casts. Row.get[T: FromSql] and get_at retain upstream decoders. Columns remain ordered, with OID/type/format metadata. Name lookup reports duplicates instead of picking the first column. Unsupported codecs remain explicit upstream errors; NUMERIC is not silently converted to Double. A SQL cast to text is an explicit application choice.

Command tags and row counts are upstream QuerySummary, not a universal insert ID or a widened/rounded number. PostgreSQL errors retain SQLSTATE, message and other diagnostic fields. Isolation/read-only/deferrable options use upstream TransactionOptions; server restrictions are reported as errors.

Clean recycling is required and validated. A pre-recycle ROLLBACK also cleans up an unmanaged transaction before upstream resets settings, temporary objects, listeners and advisory locks. The facade adds bounded admission and lifetime checks, not another connection pool. Both transaction and query operations currently drain on cancellation; upstream operation-cancel tokens/streaming are not exported by this adapter.

Results default to 10,000 rows and 16 MiB value bytes, configurable with max_rows/max_bytes. These are collected-result limits, not a hard cap on upstream protocol buffers, individual incoming messages, or peak process memory. Over-limit streams drain before the connection is discarded. Checkout defaults to 5 seconds and 128 waiters. See the shared SQL contract.

The new registry dependency also pulls moonbitlang/x@0.4.41 and tonyfettes/unicode@0.3.0; async remains 0.22.1. No npm dependency was added. The consumer and CI exercise a real database, exact values, RETURNING, cleanup, result limits and the shared conformance suite. TLS/failover configurations are not integration-tested here.

ResultTooLarge

source

pub(all) suberror ResultTooLarge

Row

source

pub struct Row {
  columns : Array[@moonbit-community/postgres/client.Column
Column]
  // private fields
}

Keep PostgreSQL column metadata and FromSql decoding. Lookup by name refuses duplicates instead of inheriting the upstream first-match behavior.

Row::get

source

fn[T : @moonbit-community/postgres/client.FromSql
FromSql] Row::get(self : Row, name : String) -> T raise

Row::get_at

source

fn[T : @moonbit-community/postgres/client.FromSql
FromSql] Row::get_at(self : Row, index : Int) -> T raise

database

source

fn database(config : @moonbit-community/postgres/pgpool.Config
Config, group : @moonbitlang/async.TaskGroup
TaskGroup[Unit], max_waiters? : Int, checkout_timeout_ms? : Int, max_rows? : Int, max_bytes? : Int) -> @Hosi121/sql_session.Database
Database[&@moonbit-community/postgres/client.ToSql
ToSql, Row, @moonbit-community/postgres/client.QuerySummary
QuerySummary, @moonbit-community/postgres/pgpool.TransactionOptions
TransactionOptions] raise

Uses one upstream pool; there is no second connection pool. Its TaskGroup must outlive the database and all borrowed sessions. Clean recycling is required so session settings and temporary objects do not leak to borrowers.

with_database

source

async fn[T] with_database(config : @moonbit-community/postgres/pgpool.Config
Config, f : async (@Hosi121/sql_session.Database
Database[&@moonbit-community/postgres/client.ToSql
ToSql, Row, @moonbit-community/postgres/client.QuerySummary
QuerySummary, @moonbit-community/postgres/pgpool.TransactionOptions
TransactionOptions]) -> T, max_waiters? : Int, checkout_timeout_ms? : Int, max_rows? : Int, max_bytes? : Int) -> T