Module: PgHero::Methods::Indexes

Included in:
Database
Defined in:
lib/pghero/methods/indexes.rb

Instance Method Summary collapse

Instance Method Details

#duplicate_indexes(indexes: nil) ⇒ Object 



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# File 'lib/pghero/methods/indexes.rb', line 171

def duplicate_indexes(indexes: nil)
  dup_indexes = []

  indexes_by_table = (indexes || self.indexes).group_by { |i| [i[:schema], i[:table]] }
  indexes_by_table.values.flatten.select { |i| i[:valid] && !i[:primary] && !i[:unique] }.each do |index|
    covering_index = indexes_by_table[[index[:schema], index[:table]]].find { |i| i[:valid] && i[:name] != index[:name] && index_covers?(i[:columns], index[:columns]) && i[:using] == index[:using] && i[:indexprs] == index[:indexprs] && i[:indpred] == index[:indpred] }
    if covering_index && (covering_index[:columns] != index[:columns] || index[:name] > covering_index[:name] || covering_index[:primary] || covering_index[:unique])
      dup_indexes << {unneeded_index: index, covering_index: covering_index}
    end
  end

  dup_indexes.sort_by { |i| ui = i[:unneeded_index]; [ui[:table], ui[:columns]] }
end

#index_bloat(min_size: nil) ⇒ Object

gist.github.com/mbanck/9976015/71888a24e464e2f772182a7eb54f15a125edf398 thanks @jberkus and @mbanck



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# File 'lib/pghero/methods/indexes.rb', line 187

def index_bloat(min_size: nil)
  min_size ||= index_bloat_bytes
  select_all <<~SQL
    WITH btree_index_atts AS (
      SELECT
        nspname, relname, reltuples, relpages, indrelid, relam,
        regexp_split_to_table(indkey::text, ' ')::smallint AS attnum,
        indexrelid as index_oid
      FROM
        pg_index
      JOIN
        pg_class ON pg_class.oid = pg_index.indexrelid
      JOIN
        pg_namespace ON pg_namespace.oid = pg_class.relnamespace
      JOIN
        pg_am ON pg_class.relam = pg_am.oid
      WHERE
        pg_am.amname = 'btree'
    ),
    index_item_sizes AS (
      SELECT
        i.nspname,
        i.relname,
        i.reltuples,
        i.relpages,
        i.relam,
        (quote_ident(s.schemaname) || '.' || quote_ident(s.tablename))::regclass AS starelid,
        a.attrelid AS table_oid, index_oid,
        current_setting('block_size')::numeric AS bs,
        /* MAXALIGN: 4 on 32bits, 8 on 64bits (and mingw32 ?) */
        CASE
          WHEN version() ~ 'mingw32' OR version() ~ '64-bit' THEN 8
          ELSE 4
        END AS maxalign,
        24 AS pagehdr,
        /* per tuple header: add index_attribute_bm if some cols are null-able */
        CASE WHEN max(coalesce(s.null_frac,0)) = 0
          THEN 2
          ELSE 6
        END AS index_tuple_hdr,
        /* data len: we remove null values save space using it fractionnal part from stats */
        sum( (1-coalesce(s.null_frac, 0)) * coalesce(s.avg_width, 2048) ) AS nulldatawidth
      FROM
        pg_attribute AS a
      JOIN
        pg_stats AS s ON (quote_ident(s.schemaname) || '.' || quote_ident(s.tablename))::regclass=a.attrelid AND s.attname = a.attname
      JOIN
        btree_index_atts AS i ON i.indrelid = a.attrelid AND a.attnum = i.attnum
      WHERE
        a.attnum > 0
      GROUP BY
        1, 2, 3, 4, 5, 6, 7, 8, 9
    ),
    index_aligned AS (
      SELECT
        maxalign,
        bs,
        nspname,
        relname AS index_name,
        reltuples,
        relpages,
        relam,
        table_oid,
        index_oid,
        ( 2 +
          maxalign - CASE /* Add padding to the index tuple header to align on MAXALIGN */
            WHEN index_tuple_hdr%maxalign = 0 THEN maxalign
            ELSE index_tuple_hdr%maxalign
          END
        + nulldatawidth + maxalign - CASE /* Add padding to the data to align on MAXALIGN */
            WHEN nulldatawidth::integer%maxalign = 0 THEN maxalign
            ELSE nulldatawidth::integer%maxalign
          END
        )::numeric AS nulldatahdrwidth, pagehdr
      FROM
        index_item_sizes AS s1
    ),
    otta_calc AS (
      SELECT
        bs,
        nspname,
        table_oid,
        index_oid,
        index_name,
        relpages,
        coalesce(
          ceil((reltuples*(4+nulldatahdrwidth))/(bs-pagehdr::float)) +
          CASE WHEN am.amname IN ('hash','btree') THEN 1 ELSE 0 END , 0 /* btree and hash have a metadata reserved block */
        ) AS otta
      FROM
        index_aligned AS s2
      LEFT JOIN
        pg_am am ON s2.relam = am.oid
    ),
    raw_bloat AS (
      SELECT
        nspname,
        c.relname AS table_name,
        index_name,
        bs*(sub.relpages)::bigint AS totalbytes,
        CASE
          WHEN sub.relpages <= otta THEN 0
          ELSE bs*(sub.relpages-otta)::bigint END
          AS wastedbytes,
        CASE
          WHEN sub.relpages <= otta
          THEN 0 ELSE bs*(sub.relpages-otta)::bigint * 100 / (bs*(sub.relpages)::bigint) END
          AS realbloat,
        pg_relation_size(sub.table_oid) as table_bytes,
        stat.idx_scan as index_scans,
        stat.indexrelid
      FROM
        otta_calc AS sub
      JOIN
        pg_class AS c ON c.oid=sub.table_oid
      JOIN
        pg_stat_user_indexes AS stat ON sub.index_oid = stat.indexrelid
    )
    SELECT
      nspname AS schema,
      table_name AS table,
      index_name AS index,
      wastedbytes AS bloat_bytes,
      totalbytes AS index_bytes,
      pg_get_indexdef(rb.indexrelid) AS definition,
      indisprimary AS primary
    FROM
      raw_bloat rb
    INNER JOIN
      pg_index i ON i.indexrelid = rb.indexrelid
    WHERE
      wastedbytes >= #{min_size.to_i}
    ORDER BY
      wastedbytes DESC,
      index_name
  SQL
end

#index_caching ⇒ Object 



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# File 'lib/pghero/methods/indexes.rb', line 13

def index_caching
  select_all <<~SQL
    SELECT
      schemaname AS schema,
      relname AS table,
      indexrelname AS index,
      CASE WHEN idx_blks_hit + idx_blks_read = 0 THEN
        0
      ELSE
        ROUND(1.0 * idx_blks_hit / (idx_blks_hit + idx_blks_read), 2)
      END AS hit_rate
    FROM
      pg_statio_user_indexes
    ORDER BY
      3 DESC, 1
  SQL
end

#index_hit_rate ⇒ Object 



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# File 'lib/pghero/methods/indexes.rb', line 4

def index_hit_rate
  select_one <<~SQL
    SELECT
      (sum(idx_blks_hit)) / nullif(sum(idx_blks_hit + idx_blks_read), 0) AS rate
    FROM
      pg_statio_user_indexes
  SQL
end

#index_usage ⇒ Object 



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# File 'lib/pghero/methods/indexes.rb', line 31

def index_usage
  select_all <<~SQL
    SELECT
      schemaname AS schema,
      relname AS table,
      CASE idx_scan
        WHEN 0 THEN 'Insufficient data'
        ELSE (100 * idx_scan / (seq_scan + idx_scan))::text
      END percent_of_times_index_used,
      n_live_tup AS estimated_rows
    FROM
      pg_stat_user_tables
    ORDER BY
      n_live_tup DESC,
      relname ASC
   SQL
end

#indexes ⇒ Object

TODO parse array properly stackoverflow.com/questions/2204058/list-columns-with-indexes-in-postgresql



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# File 'lib/pghero/methods/indexes.rb', line 128

def indexes
  indexes = select_all(<<~SQL
    SELECT
      schemaname AS schema,
      t.relname AS table,
      ix.relname AS name,
      regexp_replace(pg_get_indexdef(i.indexrelid), '^[^\\(]*\\((.*)\\)$', '\\1') AS columns,
      regexp_replace(pg_get_indexdef(i.indexrelid), '.* USING ([^ ]*) \\(.*', '\\1') AS using,
      indisunique AS unique,
      indisprimary AS primary,
      indisvalid AS valid,
      indexprs::text,
      indpred::text,
      pg_get_indexdef(i.indexrelid) AS definition
    FROM
      pg_index i
    INNER JOIN
      pg_class t ON t.oid = i.indrelid
    INNER JOIN
      pg_class ix ON ix.oid = i.indexrelid
    LEFT JOIN
      pg_stat_user_indexes ui ON ui.indexrelid = i.indexrelid
    WHERE
      schemaname IS NOT NULL
    ORDER BY
      1, 2
  SQL
  ).map { |v| v[:columns] = v[:columns].sub(") WHERE (", " WHERE ").split(", ").map { |c| unquote(c) }; v }

  # determine if any invalid indexes being created
  # hacky, but works for simple cases
  # can be a race condition, but that's fine
  invalid_indexes = indexes.select { |i| !i[:valid] }
  if invalid_indexes.any?
    create_index_queries = running_queries.select { |q| /\s*CREATE\s+INDEX\s+CONCURRENTLY\s+/i.match(q[:query]) }
    invalid_indexes.each do |index|
      index[:creating] = create_index_queries.any? { |q| q[:query].include?(index[:table]) && index[:columns].all? { |c| q[:query].include?(c) } }
    end
  end

  indexes
end

#invalid_indexes(indexes: nil) ⇒ Object 



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# File 'lib/pghero/methods/indexes.rb', line 117

def invalid_indexes(indexes: nil)
  indexes = (indexes || self.indexes).select { |i| !i[:valid] && !i[:creating] }
  indexes.each do |index|
    # map name -> index for backward compatibility
    index[:index] = index[:name]
  end
  indexes
end

#last_stats_reset_time ⇒ Object 



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# File 'lib/pghero/methods/indexes.rb', line 106

def last_stats_reset_time
  select_one <<~SQL
    SELECT
      pg_stat_get_db_stat_reset_time(oid) AS reset_time
    FROM
      pg_database
    WHERE
      datname = current_database()
  SQL
end

#missing_indexes ⇒ Object 



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# File 'lib/pghero/methods/indexes.rb', line 49

def missing_indexes
  select_all <<~SQL
    SELECT
      schemaname AS schema,
      relname AS table,
      CASE idx_scan
        WHEN 0 THEN 'Insufficient data'
        ELSE (100 * idx_scan / (seq_scan + idx_scan))::text
      END percent_of_times_index_used,
      n_live_tup AS estimated_rows
    FROM
      pg_stat_user_tables
    WHERE
      idx_scan > 0
      AND (100 * idx_scan / (seq_scan + idx_scan)) < 95
      AND n_live_tup >= 10000
    ORDER BY
      n_live_tup DESC,
      relname ASC
   SQL
end

#reset_stats ⇒ Object 



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# File 'lib/pghero/methods/indexes.rb', line 101

def reset_stats
  execute("SELECT pg_stat_reset()")
  true
end

#unused_indexes(max_scans: 50, across: []) ⇒ Object 



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# File 'lib/pghero/methods/indexes.rb', line 71

def unused_indexes(max_scans: 50, across: [])
  result = select_all_size <<~SQL
    SELECT
      schemaname AS schema,
      relname AS table,
      indexrelname AS index,
      pg_relation_size(i.indexrelid) AS size_bytes,
      idx_scan as index_scans
    FROM
      pg_stat_user_indexes ui
    INNER JOIN
      pg_index i ON ui.indexrelid = i.indexrelid
    WHERE
      NOT indisunique
      AND idx_scan <= #{max_scans.to_i}
    ORDER BY
      pg_relation_size(i.indexrelid) DESC,
      relname ASC
  SQL

  across.each do |database_id|
    database = PgHero.databases.values.find { |d| d.id == database_id }
    raise PgHero::Error, "Database not found: #{database_id}" unless database
    across_result = Set.new(database.unused_indexes(max_scans: max_scans).map { |v| [v[:schema], v[:index]] })
    result.select! { |v| across_result.include?([v[:schema], v[:index]]) }
  end

  result
end