Class: Shiba::Explain::PostgresExplain

Inherits:
Object
  • Object
show all
Defined in:
lib/shiba/explain/postgres_explain.rb

Instance Method Summary collapse

Constructor Details

#initialize(json) ⇒ PostgresExplain

Returns a new instance of PostgresExplain.



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# File 'lib/shiba/explain/postgres_explain.rb', line 6

def initialize(json)
  @json = json
  @state = {}
end

Instance Method Details

#extract_join_key_parts(cond) ⇒ Object 



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# File 'lib/shiba/explain/postgres_explain.rb', line 90

def extract_join_key_parts(cond)
  begin
    conds = Parsers::PostgresExplainIndexConditions.new(cond)
    conds.join_fields
  rescue Parsers::BadParse => e
    debugger
    {}
  end
end

#extract_used_key_parts(cond) ⇒ Object 



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# File 'lib/shiba/explain/postgres_explain.rb', line 80

def extract_used_key_parts(cond)
  begin
    conds = Parsers::PostgresExplainIndexConditions.new(cond)
    conds.fields
  rescue Parsers::BadParse => e
    debugger
    {}
  end
end

#recurse_plans(node, array) ⇒ Object 



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# File 'lib/shiba/explain/postgres_explain.rb', line 100

def recurse_plans(node, array)
  node['Plans'].each do |n|
    transform_node(n, array)
  end
end

#transform ⇒ Object 



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# File 'lib/shiba/explain/postgres_explain.rb', line 106

def transform
  plan = @json.first['Plan']
  transform_node(plan, [])
end

#transform_node(node, array) ⇒ Object 



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# File 'lib/shiba/explain/postgres_explain.rb', line 18

def transform_node(node, array)
  case node['Node Type']
  when "Limit", "LockRows", "Aggregate", "Unique", "Sort", "Hash", "ProjectSet", "Materialize"
    recurse_plans(node, array)
  when "Hash Join", "Merge Join", "Nested Loop", "BitmapOr"
    with_state(join_type: node['Node Type']) do
      recurse_plans(node, array)
    end
  when "Bitmap Heap Scan"
    with_state(table: node['Relation Name']) do
      recurse_plans(node, array)
    end
  when "Subquery Scan"
    with_state(subquery: true) do
      recurse_plans(node, array)
    end
  when "Seq Scan"
    array << {
      "table" => node["Relation Name"],
      "access_type" => "ALL",
      "key" => nil,
      "filter" => node["Filter"]
    }
  when "Index Scan", "Bitmap Index Scan", "Index Only Scan"
    table = node["Relation Name"] || @state[:table]

    if node['Index Cond']
      used_key_parts = extract_used_key_parts(node['Index Cond'])
    else
      used_key_parts = []
    end

    if @state[:join_type] == 'BitmapOr'
      access_type = "intersect"
    else
      access_type = "ref"
    end

    h = {
      "table" => node["Relation Name"] || @state[:table],
      "access_type" => access_type,
      "key" => node["Index Name"],
      "used_key_parts" => used_key_parts
    }

    if node['Node Type'] == "Index Only Scan"
      h['using_index'] = true
    end

    array << h
  when "Result"
    # TBD: What the hell is here?  seems like queries that short-circuit end up here?
    array << {
      "extra" => "No tables used"
    }
  else
    debugger
    raise "unhandled node: #{node}"
  end
  array
end

#with_state(hash) ⇒ Object 



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# File 'lib/shiba/explain/postgres_explain.rb', line 11

def with_state(hash)
  old_state = @state
  @state = @state.merge(hash)
  yield
  @state = old_state
end