Class: Gitlab::Database::QueryAnalyzers::PreventSetOperatorMismatch::Columns

Inherits:
Object
  • Object
show all
Defined in:
lib/gitlab/database/query_analyzers/prevent_set_operator_mismatch/columns.rb

Overview

Columns refer to table columns produced by queries and parts of queries. If we have ‘SELECT namespaces.id` then `id` is a column. But, we can also have `WHERE namespaces.id > 10` and `id` is also a column.

In static analysis of a SQL query a column source can be ambiguous. Such as in ‘SELECT id FROM users, namespaces. In such cases we assume `id` could come from either `users` or `namespaces`.

Class Method Summary collapse

Class Method Details

.types(select_stmt) ⇒ Object

Determine the type of each column in the select statement. Returns a Set object containing a Types enum. When an error is found parsing will return immediately.



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# File 'lib/gitlab/database/query_analyzers/prevent_set_operator_mismatch/columns.rb', line 19

def types(select_stmt)
  # Forward through any errors when the column refers to a part of the SQL query that is known to include
  # errors. For example, the column may refer to a column from a CTE that was invalid.
  return Set.new([Type::INVALID]) if References.errors?(select_stmt.all_references)

  types = Set.new

  # Resolve the type of reference for each target in the select statement.
  target_list = select_stmt.node.target_list
  targets = target_list.map(&:res_target)
  targets.each do |target|
    target_type = get_target_type(target, select_stmt)

    # A NULL target is of the form:
    # SELECT NULL::namespaces FROM namespaces
    types += if Targets.null?(target)
               # Maintain any errors but otherwise ignore this target.
               target_type & [Type::INVALID]
             else
               target_type
             end
  end

  types
end