#4871 BigDecimal comparison failure in sqlite3_test on 1.9.2-head - Ruby on Rails

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#4871 ✓resolved

BigDecimal comparison failure in sqlite3_test on 1.9.2-head

Reported by Rohit Arondekar | June 16th, 2010 @ 01:54 PM

Active Record tests in Rails master on 1.9.2-head generated the following failure:

  1) Failure:
test_add_table_with_decimals(MigrationTest) [test/cases/migration_test.rb:1035]:
<#<BigDecimal:6b4a900,'0.2718281828 45905E1',27(27)>> expected but was
<#<BigDecimal:6b4a770,'0.2718281828 4590455E1',27(27)>>.

The assert that fails:

  assert_equal BigDecimal("2.71828182845905"), b.value_of_e

My guess is that the part of the code or the function in sqlite3-ruby that converts the float stored in the DB to a BigDecimal has higher precision in 1.9.2.

Ruby version: ruby 1.9.2dev (2010-06-06 revision 28184) [x86_64-linux]
sqlite3-ruby version: 1.3.0

Let me know if any more information is required.

Comments and changes to this ticket

Aaron Patterson June 16th, 2010 @ 06:00 PM
This is a floating point rounding problem. SQLite3 stores the big decimal as a floating point value. When the float comes back out of SQLite3 and is converted to a Float in ruby is where the problem lies. The rounding rules seem to have changed from 1.8 to 1.9 such that it makes this test break.

Since it's stored as a float, we should be using assert_in_delta() for this test. I've attached a patch which fixes the test.
- your-patch-file.diff 1.1 KB
Aaron Patterson June 16th, 2010 @ 06:01 PM
- Tag changed from “rails 3, 1.9.2, activerecord, sqlite3” to “rails 3, 1.9.2, activerecord, patch, sqlite3”
Carl Lerche June 16th, 2010 @ 06:10 PM
- State changed from “new” to “committed”
Applied
Repository June 16th, 2010 @ 06:11 PM
- State changed from “committed” to “resolved”
(from [8e56085817e752bb361738ec6ca7362a3398ed77]) use assert_in_delta() for floating point comparisons in tests [#4871 state:resolved]

Signed-off-by: Carl Lerche carllerche@mac.com
http://github.com/rails/rails/commit/8e56085817e752bb361738ec6ca736...