pg-lsn

node-pg-lsn

Constants and functions for working with postgres xlog positions. This module makes a number of assumptions about the format of xlog positions. It's not totally clear that this is a committed Postgres interface, but it seems to be true.

We assume that postgres xlog positions are represented as strings of the form:

filepart/offset		e.g., "0/17BB660"

where both "filepart" and "offset" are hexadecimal numbers. xlog position F1/O1 is at least as new as F2/O2 if (F1 > F2) or (F1 == F2 and O1 >= O2). We try to avoid assuming that they're zero-padded (i.e., that a simple string comparison might do the right thing). We also don't make any assumptions about the size of each file, which means we can't compute the actual difference between two positions.

Usage

var assert = require('assert');
var lsn = require('pg-lsn');

var locationOne = '2D7/0';
var locationTwo = '2D6/FEFFE770';
var comparison = lsn.xlogCompare(locationOne, locationTwo);

if (comparison === 0) {
    console.log('locations are the same');
} else if(comparison > 0) {
    console.log('locationOne is greater than locationTwo');
} else {
    assert.ok(comparison < 0);
    console.log('locationOne is less than locationTwo');
}