Class: Benedictus::Heuristics::SeqScanOnLargeTable

Inherits:
Base
  • Object
show all
Defined in:
lib/benedictus/heuristics/seq_scan_on_large_table.rb

Constant Summary collapse

DEFAULT_THRESHOLD = 
10_000

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from Base

apply

Constructor Details

#initialize(threshold: DEFAULT_THRESHOLD) ⇒ SeqScanOnLargeTable

Returns a new instance of SeqScanOnLargeTable.



12
13
14
15
 
# File 'lib/benedictus/heuristics/seq_scan_on_large_table.rb', line 12

def initialize(threshold: DEFAULT_THRESHOLD)
  super()
  @threshold = threshold
end

Class Method Details

.config_key ⇒ Object 



8
9
10
 
# File 'lib/benedictus/heuristics/seq_scan_on_large_table.rb', line 8

def self.config_key
  :seq_scan_threshold
end

Instance Method Details

#apply(node) ⇒ Object 



17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
 
# File 'lib/benedictus/heuristics/seq_scan_on_large_table.rb', line 17

def apply(node)
  return [] unless node.node_type == "Seq Scan"
  return [] unless node.plan_rows && node.plan_rows > @threshold

  relation = node.relation_name || "this table"
  rows     = node.plan_rows
  [
    warning(
      severity: :critical,
      code: :seq_scan_on_large_table,
      message: "Seq Scan on a table with ~#{rows.to_i} estimated rows",
      suggestion: "Consider adding an index that matches the filter on `#{relation}`."
    )
  ]
end