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e1117155ae
Consider a system where one component is scheduling tasks that yield streams, and passing them to (unknown) clients for consumption. It would be useful for the scheduler to know that the query underlying the stream is completed (so it can continue on to it's next task) without having to wait for the consumer to finish reading all results.
109 lines
2.3 KiB
JavaScript
109 lines
2.3 KiB
JavaScript
var assert = require('assert')
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var Readable = require('stream').Readable
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var path = require('path')
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var pgdir = false
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try {
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pgdir = path.dirname(require.resolve('pg'))
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} catch (e) {
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pgdir = path.dirname(require.resolve('pg.js'))
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if(!pgdir) {
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throw new Error("Please install either `pg` or `pg.js` to use this module")
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}
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pgdir = path.join(pgdir, 'lib')
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}
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var Result = require(path.join(pgdir, 'result'))
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var utils = require(path.join(pgdir, 'utils'))
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var QueryStream = module.exports = function(text, values, options) {
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options = options || { }
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Readable.call(this, {
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objectMode: true,
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highWaterMark: options.highWaterMark || 1000
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})
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this.text = text
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assert(this.text, 'text cannot be falsy')
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this.values = (values || []).map(utils.prepareValue)
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this.name = ''
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this._result = new Result()
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this.batchSize = options.batchSize || 100
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this._idle = true
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}
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require('util').inherits(QueryStream, Readable)
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QueryStream.prototype._read = function(n) {
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this._getRows(n)
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}
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QueryStream.prototype._getRows = function(count) {
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var con = this.connection
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if(!this._idle || !this.connection) return;
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this._idle = false
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con.execute({
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portal: '',
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rows: count
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}, true)
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con.flush()
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}
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QueryStream.prototype.submit = function(con) {
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//save reference to connection
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this.connection = con
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var name = this.name
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con.parse({
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text: this.text,
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name: name,
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types: []
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}, true)
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con.bind({
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portal: '',
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statement: name,
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values: this.values,
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binary: false
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}, true)
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con.describe({
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type: 'P',
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name: name
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}, true)
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this._getRows(this.batchSize)
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}
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QueryStream.prototype.handleRowDescription = function(msg) {
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this._result.addFields(msg.fields)
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}
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QueryStream.prototype.handleDataRow = function(msg) {
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var row = this._result.parseRow(msg.fields)
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this._more = this.push(row)
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}
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QueryStream.prototype.handlePortalSuspended = function(msg) {
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this._idle = true
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if(this._more) {
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this._getRows(this.batchSize)
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}
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}
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QueryStream.prototype.handleCommandComplete = function(msg) {
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this.connection.sync()
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}
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QueryStream.prototype.handleReadyForQuery = function() {
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this.emit('close')
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this.push(null)
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}
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QueryStream.prototype.handleError = function(err) {
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this.connection.sync()
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this.emit('error', err)
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}
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