pglite-socket: crash when creating a large enum value.

[itsWill]

I have a large enum value within my application with approx 1400~ values.

When it runs as a single CREATE TYPE public.big_enum as ENUM the database crashes with 2025-10-18 21:22:47.645 GMT [0] FATAL: terminating connection because protocol synchronization was lost

However when I break the enum into individual:

ALTER TYPE public.big_enum ADD VALUE 'rf_0000002';
ALTER TYPE public.big_enum ADD VALUE 'rf_0000003';

The db executes them without a problem.

Steps to Repdroduce:

Create a schema.sql file with entries up to 1000 values:

CREATE TYPE public.big_enum AS ENUM (
  'rf_0000001',
  'rf_0000002',
  'rf_0000003',
  'rf_0000004',
  'rf_0000005',
  'rf_0000006',
  'rf_0000007',
 ......
)

Run the database: npx pglite-server --path=/tmp/.s.PGSQL.5432 --debug=5 -d data

Load the schema file in through PGSSLMODE=disable psql -h /tmp -f schema.sql

The database will crash.

Converting the schema to individual ALTER TABLE statements then works.

I observed the same issue when a large insert.

[tdrz]

Thank you for this @itsWill !

One thing to try out would be to do the same insert directly with PGlite (ie without the pglite-server) and see if it still crashes.

[itsWill]

Confirmed it works in PGLite with the following script:

import { PGlite } from '@electric-sql/pglite'

async function main() {
    const db = new PGlite()

    await db.query(`
    CREATE TYPE public.big_enum AS ENUM (
    'rf_0000001',
    'rf_0000002',
     ..... 
    'rf_0001000'
    );`)

    console.log("create big enum succeeded")

    let result = await db.query(`
        SELECT unnest(enum_range(NULL::public.big_enum)) AS value;
    `)
   
    console.log(`returned rows: ${result.rows.length}`)

    result = await db.query(`
        CREATE TABLE public.enum_samples (id BIGSERIAL PRIMARY KEY, tag public.big_enum NOT NULL)
    `)

    console.log("created test table")

    const labels = Array.from({ length: 1000 }, (_, i) => `rf_${String(i + 1).padStart(7, '0')}`);
    const placeholders = labels.map((_, i) => `(CAST($${i + 1} AS public.big_enum))`).join(', ');
    const largeInsert = `INSERT INTO public.enum_samples (tag) VALUES ${placeholders}`;
    const res = await db.query(largeInsert, labels);
    console.log(`Completed insert affected rows: ${res.affectedRows}`);
}

main();

The issue is on the socket-server side.

[tdrz]

Thank you @itsWill this helps!

Will try to address it in a timely manner.

[electric-al]

I am also seeing a similar issue. Basically any statement >64k (0xffff bytes) gets split into 2 tcp packets, and this code line https://github.com/electric-sql/pglite/blob/main/packages/pglite-socket/src/index.ts#L111 sends it straight to be processed as raw request.

I think that the TCP buffers need to be joined before this happens somehow? The max length of a PG message is defined by the 32bit length field, but each TCP packet is max 64k. Example with --debug=5:

[electric-al]

I will try to send a proper PR later, but this worked for me. This solves the error.

    let messageBuffer: Buffer = new Buffer(0);
    let bytesRemaining = 0;

    // Setup event handlers
    this.log(`attach: setting up socket event handlers`);
    socket.on('data', async data => {
      if (bytesRemaining <= 0) {
        if (data[0] === 'Q'.charCodeAt(0)) {
          bytesRemaining = data.readUInt32BE(1);
        } else {
          bytesRemaining = 0;
        }
      }

      messageBuffer = Buffer.concat([messageBuffer, data]);
      bytesRemaining -= data.length;

      if (bytesRemaining <= 0) {
        try {
          const result = await this.handleData(messageBuffer);
          messageBuffer = new Buffer(0);
          this.log(`socket on data sent: ${result} bytes`);
        } catch (err) {
          this.log('socket on data error: ', err);
        }
      }
    });```

[tdrz]

Probably will be fixed once #873 is deployed.

[tdrz]

Done in #873