#91 fix error when snowflake returns empty result (#92)

CORE-885

Author: joycelau1

CHANGELOG.md

@@ -1,6 +1,10 @@
 # Change Log
 All notable changes to this project will be documented in this file using [Semantic Versioning](http://semver.org/).
 
+## [0.4.2] - 2019-09-25
+### Fixed
+- [Error when Snowflake query returns empty result set](https://github.com/lumoslabs/aleph/issues/91)
+
 ## [0.4.1] - 2019-09-10
 ### Fixed
 - [Bug fixes for v0.4.0](https://github.com/lumoslabs/aleph/pull/89) 
@@ -23,16 +27,15 @@ All notable changes to this project will be documented in this file using [Seman
 - [Site wide, saved filter for schema](https://github.com/lumoslabs/aleph/issues/38)
 
 ### Fixed
-- [Use trusty for travis](https://github.com/lumoslabs/aleph/issues/67)
+- [Use trusty for travis](https://github.com/lumoslabs/al eph/issues/67)
 - [Display 24-hour format](https://github.com/lumoslabs/aleph/issues/53)
 - [Schema search should be able to handle numbers](https://github.com/lumoslabs/aleph/issues/59)
 - [Clean up /tmp result files when query fails](https://github.com/lumoslabs/aleph/issues/37)
 - [Increase schema query reties](https://github.com/lumoslabs/aleph/issues/64)
 
 ## [0.1.0] - 2017-04-27
 ### Features
-- [Auto-complete on dot](https://github.com/lumoslabs/aleph/issues/48)
-
+- [Auto-complete on dot](https://github.com/lumoslabs/aleph/issues/48)auser
 ### Fixed
 - [change retry configuration for schema query](https://github.com/lumoslabs/aleph/issues/46)
 

aleph.gemspec

@@ -1,11 +1,11 @@
 Gem::Specification.new do |s|
   s.name        = 'aleph_analytics'
-  s.version     = '0.4.1'
-  s.date        = '2019-09-10'
+  s.version     = '0.4.2'
+  s.date        = '2019-09-25'
   s.summary     = 'Redshift/Snowflake analytics platform'
   s.description = 'The best way to develop and share queries/investigations/results within an analytics team'
-  s.authors     = ['Andrew Xue', 'Rob Froetscher']
-  s.email       = 'andrew@lumoslabs.com'
+  s.authors     = ['Andrew Xue', 'Rob Froetscher', 'Joyce Lau']
+  s.email       = 'eng-data@lumoslabs.com'
   s.files       = Dir.glob('{app,bin,lib,config,vendor}/**/*') +
                   # need to find the hidden sprockets manifest in public/assets
                   Dir.glob('public/assets/**/*', File::FNM_DOTMATCH) +

app/models/query_execution.rb

@@ -73,9 +73,16 @@ def self.query_snowflake(connection, body, result, sample_callback)
       location = File.join(connection.unload_target, result.current_result_filename)
       sql = SNOWFLAKE_UNLOAD_SQL % {location: location, query: body, max_file_size: connection.max_file_size}
       row = connection.connection.fetch(sql).first
-      row_count = row[:rows_unloaded]
+      row_count = row[:rows_unloaded].to_i
 
-      headers, samples = CsvSerializer.load_from_s3_file(result.current_result_s3_key, NUM_SAMPLE_ROWS)
+      if row_count.zero?
+        # snowflake unload does not create a file if query returns empty result set; create an empty file
+        headers = ['']
+        samples = []
+        ResultCsvGenerator.new(result.id, headers, true)
+      else
+        headers, samples = CsvSerializer.load_from_s3_file(result.current_result_s3_key, NUM_SAMPLE_ROWS)
+      end
 
       result.headers = headers
       result.save!

lib/result_csv_generator.rb

@@ -3,10 +3,15 @@
 class ResultCsvGenerator
   attr_accessor :csv
 
-  def initialize(result_id, headers)
+  def initialize(result_id, headers, create_empty = false)
     @result_id = result_id
     @headers = headers
     @csv_service = CsvService.new(@result_id)
+
+    if create_empty
+      setup_csv.call()
+      finish_csv.call(0)
+    end
   end
 
   def callbacks