Use a PostgreSQL result cursor from node with an easy to use API.
Sometimes you need to itterate through a table in chunks. It's extremely inefficient to use hand-crafted
OFFSET queries to do this.
PostgreSQL provides built-in functionality to fetch a "cursor" to your results and page through the cursor efficiently fetching chunks of the results with full MVCC compliance.
This actually ends up pairing very nicely with node's asyncness and handling a lot of data. PostgreSQL is rad.
var Cursor = require'pg-cursor'var pg = require'pg'pgconnect//imagine some_table has 30,000,000 results where prop > 100//lets create a query cursor to efficiently deal with the huge result setvar cursor = clientquery'SELECT * FROM some_table WHERE prop > $1' 100//read the first 100 rows from this cursorcursorread100iferr//cursor error - release the client//normally you'd do app-specific error handling herereturn doneerr//when the cursor is exhausted and all rows have been returned//all future calls to `cursor#read` will return an empty row array//so if we received no rows, release the client and be doneif!rowslength return done//do something with your rows//when you're ready, read another chunk from//your resultcursorread2000//I think you get the picture, yeah?//if you dont...open an issue - I'd love to help you out!//Also - you probably want to use some sort of async or promise library to deal with paging//through your cursor results. node-pg-cursor makes no asumptions for you on that front.;
Creates an instance of a query cursor. Pass this instance to node-postgres
rowCount rows from the cursor instance. The
If the cursor has read to the end of the result sets all subsequent calls to
cursor#read will return a 0 length array of rows. I'm open to other ways to signal the end of a cursor, but this has worked out well for me so far.
Closes the backend portal before itterating through the entire result set. Useful when you want to 'abort' out of a read early but continue to use the same client for other queries after the cursor is finished.
$ npm install pg-cursor
note: this depends on either
npm install pg or
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Copyright (c) 2013 Brian M. Carlson
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