feat: add maxResultSize limit

Author: avallete

Diff for: packages/pg/lib/client.js

@@ -52,6 +52,7 @@ class Client extends EventEmitter {
         keepAlive: c.keepAlive || false,
         keepAliveInitialDelayMillis: c.keepAliveInitialDelayMillis || 0,
         encoding: this.connectionParameters.client_encoding || 'utf8',
+        maxResultSize: c.maxResultSize,
       })
     this.queryQueue = []
     this.binary = c.binary || defaults.binary

Diff for: packages/pg/lib/connection.js

@@ -27,6 +27,8 @@ class Connection extends EventEmitter {
     this.ssl = config.ssl || false
     this._ending = false
     this._emitMessage = false
+    this._maxResultSize = config.maxResultSize
+    this._currentResultSize = 0
     var self = this
     this.on('newListener', function (eventName) {
       if (eventName === 'message') {
@@ -108,6 +110,17 @@ class Connection extends EventEmitter {
   }
 
   attachListeners(stream) {
+    var self = this
+    // Use the appropriate implementation based on whether maxResultSize is enabled
+    if (self._maxResultSize && self._maxResultSize > 0) {
+      this._attachListenersWithSizeLimit(stream)
+    } else {
+      this._attachListenersStandard(stream)
+    }
+  }
+
+  // Original implementation with no overhead
+  _attachListenersStandard(stream) {
     parse(stream, (msg) => {
       var eventName = msg.name === 'error' ? 'errorMessage' : msg.name
       if (this._emitMessage) {
@@ -117,6 +130,41 @@ class Connection extends EventEmitter {
     })
   }
 
+  // Implementation with size limiting logic
+  _attachListenersWithSizeLimit(stream) {
+    parse(stream, (msg) => {
+      var eventName = msg.name === 'error' ? 'errorMessage' : msg.name
+
+      // Only track data row messages for result size
+      if (msg.name === 'dataRow') {
+        // Approximate size by using message length
+        const msgSize = msg.length || 1024 // Default to 1KB if we don't have lenght info
+        this._currentResultSize += msgSize
+
+        // Check if we've exceeded the max result size
+        if (this._currentResultSize > this._maxResultSize) {
+          const error = new Error('Query result size exceeded the configured limit')
+          error.code = 'RESULT_SIZE_EXCEEDED'
+          error.resultSize = this._currentResultSize
+          error.maxResultSize = this._maxResultSize
+          this.emit('errorMessage', error)
+          this.end() // Terminate the connection
+          return
+        }
+      }
+
+      // Reset counter on query completion
+      if (msg.name === 'readyForQuery') {
+        this._currentResultSize = 0
+      }
+
+      if (this._emitMessage) {
+        this.emit('message', msg)
+      }
+      this.emit(eventName, msg)
+    })
+  }
+
   requestSsl() {
     this.stream.write(serialize.requestSsl())
   }

Diff for: packages/pg/lib/defaults.js

@@ -70,6 +70,8 @@ module.exports = {
   keepalives: 1,
 
   keepalives_idle: 0,
+  // maxResultSize limit of a request before erroring out
+  maxResultSize: undefined,
 }
 
 var pgTypes = require('pg-types')

Diff for: packages/pg/lib/native/client.js

@@ -26,6 +26,9 @@ var Client = (module.exports = function (config) {
     types: this._types,
   })
 
+  // Store maxResultSize configuration
+  this._maxResultSize = config.maxResultSize
+
   this._queryQueue = []
   this._ending = false
   this._connecting = false
@@ -100,6 +103,9 @@ Client.prototype._connect = function (cb) {
       // set internal states to connected
       self._connected = true
 
+      // Add a reference to the client for error bubbling
+      self.native.connection = self
+
       // handle connection errors from the native layer
       self.native.on('error', function (err) {
         self._queryable = false

Diff for: packages/pg/lib/native/query.js

@@ -56,6 +56,17 @@ NativeQuery.prototype.handleError = function (err) {
       err[normalizedFieldName] = fields[key]
     }
   }
+
+  // For maxResultSize exceeded errors, make sure we emit the error to the client too
+  if (err.code === 'RESULT_SIZE_EXCEEDED') {
+    if (this.native && this.native.connection) {
+      // Need to emit the error on the client/connection level too
+      process.nextTick(() => {
+        this.native.connection.emit('error', err)
+      })
+    }
+  }
+
   if (this.callback) {
     this.callback(err)
   } else {
@@ -89,6 +100,9 @@ NativeQuery.prototype.submit = function (client) {
   this.native = client.native
   client.native.arrayMode = this._arrayMode
 
+  // Get the maxResultSize from the client if it's set
+  this._maxResultSize = client._maxResultSize
+
   var after = function (err, rows, results) {
     client.native.arrayMode = false
     setImmediate(function () {
@@ -100,6 +114,30 @@ NativeQuery.prototype.submit = function (client) {
       return self.handleError(err)
     }
 
+    // Check the result size if maxResultSize is configured
+    if (self._maxResultSize) {
+      // Calculate result size (rough approximation)
+      let resultSize = 0
+
+      // For multiple result sets
+      if (results.length > 1) {
+        for (let i = 0; i < rows.length; i++) {
+          resultSize += self._calculateResultSize(rows[i])
+        }
+      } else if (rows.length > 0) {
+        resultSize = self._calculateResultSize(rows)
+      }
+
+      // If the size limit is exceeded, generate an error
+      if (resultSize > self._maxResultSize) {
+        const error = new Error('Query result size exceeded the configured limit')
+        error.code = 'RESULT_SIZE_EXCEEDED'
+        error.resultSize = resultSize
+        error.maxResultSize = self._maxResultSize
+        return self.handleError(error)
+      }
+    }
+
     // emit row events for each row in the result
     if (self._emitRowEvents) {
       if (results.length > 1) {
@@ -166,3 +204,59 @@ NativeQuery.prototype.submit = function (client) {
     client.native.query(this.text, after)
   }
 }
+
+// Helper method to estimate the size of a result set
+NativeQuery.prototype._calculateResultSize = function (rows) {
+  let size = 0
+
+  // For empty results, return 0
+  if (!rows || rows.length === 0) {
+    return 0
+  }
+
+  // For array mode, calculate differently
+  if (this._arrayMode) {
+    // Just use a rough approximation based on number of rows
+    return rows.length * 100
+  }
+
+  // For each row, approximate its size
+  for (let i = 0; i < rows.length; i++) {
+    const row = rows[i]
+
+    // Add base row size
+    size += 24 // Overhead per row
+
+    // Add size of each column
+    for (const key in row) {
+      if (Object.prototype.hasOwnProperty.call(row, key)) {
+        const value = row[key]
+
+        // Add key size
+        size += key.length * 2 // Assume 2 bytes per character
+
+        // Add value size based on type
+        if (value === null || value === undefined) {
+          size += 8
+        } else if (typeof value === 'string') {
+          size += value.length * 2 // Assume 2 bytes per character
+        } else if (typeof value === 'number') {
+          size += 8
+        } else if (typeof value === 'boolean') {
+          size += 4
+        } else if (value instanceof Date) {
+          size += 8
+        } else if (Buffer.isBuffer(value)) {
+          size += value.length
+        } else if (Array.isArray(value)) {
+          size += 16 + value.length * 8
+        } else {
+          // For objects, use a rough estimate
+          size += 32 + JSON.stringify(value).length * 2
+        }
+      }
+    }
+  }
+
+  return size
+}

Diff for: packages/pg/test/integration/client/max-result-size-tests.js

@@ -0,0 +1,131 @@
+'use strict'
+const helper = require('../test-helper')
+const pg = helper.pg
+const assert = require('assert')
+
+process.on('unhandledRejection', function (e) {
+  console.error(e, e.stack)
+  process.exit(1)
+})
+
+const suite = new helper.Suite()
+
+suite.test('maxResultSize limit triggers error', (cb) => {
+  // Check if we're running with the native client
+  const isNative = helper.args.native
+  console.log(isNative ? 'Testing with native client' : 'Testing with JavaScript client')
+
+  // Create a pool with a very small result size limit
+  const pool = new pg.Pool({
+    maxResultSize: 100, // Very small limit (100 bytes)
+    ...helper.args,
+  })
+
+  let sizeExceededErrorSeen = false
+
+  pool.on('error', (err) => {
+    console.log('Pool error:', err.message, err.code)
+  })
+
+  pool
+    .connect()
+    .then((client) => {
+      // Set up client error listener for error events
+      client.on('error', (err) => {
+        console.log('Client error event:', err.message, err.code)
+
+        // If we get any size exceeded error, mark it
+        if (err.code === 'RESULT_SIZE_EXCEEDED' || err.message === 'Query result size exceeded the configured limit') {
+          sizeExceededErrorSeen = true
+        }
+      })
+
+      return client
+        .query('CREATE TEMP TABLE large_result_test(id SERIAL, data TEXT)')
+        .then(() => {
+          // Insert rows that will exceed the size limit when queried
+          const insertPromises = []
+          for (let i = 0; i < 20; i++) {
+            // Each row will have enough data to eventually exceed our limit
+            const data = 'x'.repeat(50)
+            insertPromises.push(client.query('INSERT INTO large_result_test(data) VALUES($1)', [data]))
+          }
+          return Promise.all(insertPromises)
+        })
+        .then(() => {
+          console.log('Running query that should exceed size limit...')
+
+          return client
+            .query('SELECT * FROM large_result_test')
+            .then(() => {
+              throw new Error('Query should have failed due to size limit')
+            })
+            .catch((err) => {
+              console.log('Query error caught:', err.message, err.code)
+
+              // Both implementations should throw an error with this code
+              assert.equal(err.code, 'RESULT_SIZE_EXCEEDED', 'Error should have RESULT_SIZE_EXCEEDED code')
+
+              // Give time for error events to propagate
+              return new Promise((resolve) => setTimeout(resolve, 100)).then(() => {
+                // Verify we saw the error event
+                assert(sizeExceededErrorSeen, 'Should have seen the size exceeded error event')
+
+                return client.query('DROP TABLE IF EXISTS large_result_test').catch(() => {
+                  /* ignore cleanup errors */
+                })
+              })
+            })
+        })
+        .then(() => {
+          client.release()
+          pool.end(cb)
+        })
+        .catch((err) => {
+          console.error('Test error:', err.message)
+          client.release()
+          pool.end(() => cb(err))
+        })
+    })
+    .catch((err) => {
+      console.error('Connection error:', err.message)
+      pool.end(() => cb(err))
+    })
+})
+
+suite.test('results under maxResultSize limit work correctly', (cb) => {
+  // Create a pool with a reasonably large limit
+  const pool = new pg.Pool({
+    maxResultSize: 10 * 1024, // 10KB is plenty for small results
+    ...helper.args,
+  })
+
+  pool
+    .connect()
+    .then((client) => {
+      return client
+        .query('CREATE TEMP TABLE small_result_test(id SERIAL, data TEXT)')
+        .then(() => {
+          return client.query('INSERT INTO small_result_test(data) VALUES($1)', ['small_data'])
+        })
+        .then(() => {
+          return client.query('SELECT * FROM small_result_test').then((result) => {
+            assert.equal(result.rows.length, 1, 'Should get 1 row')
+            assert.equal(result.rows[0].data, 'small_data', 'Data should match')
+
+            return client.query('DROP TABLE small_result_test')
+          })
+        })
+        .then(() => {
+          client.release()
+          pool.end(cb)
+        })
+        .catch((err) => {
+          client.release()
+          pool.end(() => cb(err))
+        })
+    })
+    .catch((err) => {
+      pool.end(() => cb(err))
+    })
+})