Rails

I was deep in a performance optimization flow when I stumbled upon this part in a ruby-prof graph:

- 17.59% (73.45%) SomeTable::GeneratedAttributeMethods#some_attribute [30263106 calls, 44665545 total]
  - 15.24% (86.62%) ActiveRecord::AttributeMethods::Read#_read_attribute [30263106 calls, 49437307 total]
    - 11.82% (77.58%) ActiveModel::AttributeSet#fetch_value [30263106 calls, 49068748 total]
      - 5.44% (46.06%) ActiveModel::AttributeSet#[] [30263106 calls, 49303667 total]
        - 2.32% (42.58%) Hash#[] [30263106 calls, 72892138 total]
      - 2.05% (17.36%) ActiveModel::Attribute#value [30263106 calls, 49274896 total]

ActiveRecord stores attributes internally in a hash, which is more expensive than I expected.

Here’s a small bug we recently encountered in production. Occasionally, PDF generation jobs would fail, and the cause turned out to be a small oversight when designing database tables.

The PDF metadata is stored in a table, and the column for file size was defined as integer, also known as int4.

Since this data type is signed in Postgres, those 4 bytes only allow for files up to 2.1 GB (2 147 483 647 bytes). You might think, 2^31 bytes ought to be enough for everybody … except apparently for our PDFs.