diff options
Diffstat (limited to 'doc/development/ordering_table_columns.md')
| -rw-r--r-- | doc/development/ordering_table_columns.md | 12 |
1 files changed, 8 insertions, 4 deletions
diff --git a/doc/development/ordering_table_columns.md b/doc/development/ordering_table_columns.md index b68602ea30d..18788d0b86e 100644 --- a/doc/development/ordering_table_columns.md +++ b/doc/development/ordering_table_columns.md @@ -1,5 +1,10 @@ # Ordering Table Columns in PostgreSQL +For GitLab we require that columns of new tables are ordered to use the +least amount of space. An easy way of doing this is to order them based on the +type size in descending order with variable sizes (`text`, `varchar`, arrays, +`json`, `jsonb`, and so on) at the end. + Similar to C structures the space of a table is influenced by the order of columns. This is because the size of columns is aligned depending on the type of the following column. Let's consider an example: @@ -40,10 +45,9 @@ In these examples, the `id` and `user_id` columns are packed together, which means we only need 8 bytes to store _both_ of them. This in turn means each row will require 8 bytes less space. -For GitLab we require that columns of new tables are ordered based to use the -least amount of space. An easy way of doing this is to order them based on the -type size in descending order with variable sizes (`text`, `varchar`, arrays, -`json`, `jsonb`, and so on) at the end. +Note: **NOTE:** +Since Ruby on Rails 5.1, the default data type for IDs is `bigint`, which uses 8 bytes. +We are using `integer` in the examples to showcase a more realistic reordering scenario. ## Type Sizes |