Schnellzugriff per Seek, FNV-1a-Hash, Dezimalrechnung für Summen und /act

search, seek, delete und update.rdb lesen bei -mh, -mi, -mr nur Indexeintrag
und Satz. Hashindizes (.h) müssen neu gebaut werden. total, mean, subtotal
und die /act-Befehle rechnen mit BigDecimal, gerundet wird halb auf.

CHANGELOG.md

@@ -17,6 +17,11 @@ folgen [Semantic Versioning](https://semver.org/lang/de/). Die Version steht in
 - `gregorian -u` schreibt den Monat ohne führende Null (`6/01/89`), wie im Handbuch.
 - `mean` schreibt einen ganzzahligen Mittelwert ohne `.00` (`4786`, Handbuch S. 26).
 
+### Verbessert
+- Schnellzugriff: `search`, `seek`, `delete` und `update.rdb` lesen bei `-mh`, `-mi` und `-mr` nur noch den Indexeintrag und den einen Satz (Seek auf Byte-Positionen, bei `.i` Halbierung über die Datei), nicht mehr Tabelle und Index vollständig. `Data` liest die Zeilen erst, wenn eine Methode alle braucht.
+- Die Hashfunktion ist FNV-1a statt der Bytesumme. Vorher fielen 3000 fünfstellige Nummern in 30 Plätze (größter Eimer 223), jetzt liegt der größte Eimer bei etwa 4. **Hashindizes (`.h`) müssen neu gebaut werden** (`index -mh`).
+- `total`, `mean`, `subtotal` und die /act-Befehle rechnen mit `BigDecimal` statt `Float`: `0.1 + 0.2 + 0.7` ergibt `1.0`, Beträge summieren sich auf den Rappen genau, und es wird kaufmännisch gerundet (halb auf).
+
 ### Sicherheit
 - `report`: Spaltenwerte in `<!befehl <Spalte>!>` wurden unmaskiert in einen Shell-Aufruf eingesetzt, eine Zelle konnte so Befehle ausführen. Sie werden jetzt mit `Shellwords.escape` eingesetzt.
 - `screen`: Spaltennamen, die keine gültigen Shell-Variablennamen sind, brechen mit einer Meldung ab, statt ins erzeugte Skript zu gelangen.

README.md

@@ -13,7 +13,7 @@ sind nach dem Handbuch neu geschrieben.
 mise trust            # einmal nach dem Clone: mise.toml freigeben
 mise install          # Ruby 3.4
 mise run install      # legt die Symlinks row, column, total ... in bin/ an
-mise run test         # 126 Tests und die Beispiele aus dem Handbuch
+mise run test         # 131 Tests und die Beispiele aus dem Handbuch
 ```
 
 Ohne `mise trust` brechen in einem frisch geklonten Ordner alle `mise`-Befehle ab.
@@ -243,8 +243,10 @@ er nicht mehr passt (außer mit `-a`). Beide halten die Indizes aktuell.
   Beispiele aus den Man-Pages sind als Tests enthalten (`test/rdb_test.rb`), die aus
   dem Lehrbuch in `demo/handbuch/` (`test/handbuch_test.rb`).
 - Die Indexdateien sind dem Original nachgebaut, aber nicht gleich (Handbuch S. 103–108):
-  die Hashtabelle `.h` hat 2n statt 2n+1 Plätze, und in `.i` steht der Schlüssel vor
-  dem Offset statt dahinter. Alte /rdb-Indizes muss man neu bauen.
+  die Hashtabelle `.h` hat 2n statt 2n+1 Plätze (Hashfunktion FNV-1a), und in `.i` steht der
+  Schlüssel vor dem Offset statt dahinter. Alte /rdb-Indizes und `.h`-Dateien früherer
+  Versionen dieses Nachbaus muss man neu bauen.
+- Summen, Mittelwerte und /act-Beträge sind Dezimalzahlen (`BigDecimal`), gerundet wird halb auf.
 - Dateien, die kein UTF-8 sind, liest `rdb` als Latin-1 und schreibt sie als UTF-8. Fehler
   erscheinen als eine Zeile; mit `RDB_DEBUG=1` kommt der Ruby-Backtrace. Werte mit Tab oder
   Zeilenumbruch lehnen `append`, `enter`, `replace` und `ve` ab.

demo/testall.old

@@ -659,7 +659,7 @@ Item	Amount	Cost	Value	Description
 $ echo 5 | seek inventory Item
 172 204 0 8
 $ echo 5 | seek -mh inventory Item
-172 204 113 122
+172 204 104 113
 ## searchtree: is Sally an ancestor of Jane?  (needs a table of Parent, Child)
 $ searchtree parent Sally Jane Parent Child
 TRUE

doc/review.md

@@ -74,14 +74,14 @@ Index ohne Entsprechung in der Suche offen.
 
 ## Verbesserungspotential
 
-1. **Indexe sind nicht schnell.** Jede Suche liest Tabelle und Indexdatei
+1. **Indexe sind nicht schnell. — Behoben** (Seek statt Volllesen, lazy `Data`). Ursprünglich: Jede Suche liest Tabelle und Indexdatei
    komplett ([fast.rb:151](../lib/rdb/fast.rb), [fast.rb:171](../lib/rdb/fast.rb),
    `Data.new` pro Schlüssel in `delete`/`update.rdb`): O(n) pro Schlüssel. Abhilfe:
    mit `seek`/`pread` direkt an der Fixbreiten-Position lesen.
-2. **Schlechte Hash-Funktion** ([fast.rb:68](../lib/rdb/fast.rb)):
+2. **Schlechte Hash-Funktion — Behoben** (FNV-1a, größter Eimer 4). Ursprünglich: ([fast.rb:68](../lib/rdb/fast.rb)):
    `bytes.sum % slots`. Bestätigt: 3000 fünfstellige Nummern landen in 30 Slots,
    größter Bucket 223. Abhilfe: FNV-1a o. Ä., Primzahl-Slotzahl.
-3. **Geld in `Float`** ([act.rb:11](../lib/rdb/cmd/act.rb), `to_f` im /act-Teil
+3. **Geld in `Float` — Behoben** (`BigDecimal` in `total`/`mean`/`subtotal` und /act). Ursprünglich: ([act.rb:11](../lib/rdb/cmd/act.rb), `to_f` im /act-Teil
    und in `total`). Abhilfe: `BigDecimal` oder ganzzahlige Rappen.
 4. **awk-Brücke** ([env.rb:119-138](../lib/rdb/env.rb)): ganze Tabelle als String
    durch `capture3`, kein Streaming; handgeschriebener Parser erkennt Strings und
@@ -98,5 +98,5 @@ Index ohne Entsprechung in der Suche offen.
 
 ## Empfohlene Reihenfolge
 
-Schwachstellen und Fehler sind erledigt. Weiter mit: Hash-Funktion und
-Index-Lesezugriffe (Verbesserung 1 und 2), dann Float-Geld.
+Schwachstellen, Fehler und Verbesserung 1–3 sind erledigt. Offen sind 4–8: die
+awk-Brücke, globale Methoden auf `Object`, doppelter Code, Testlaufzeit, Repo-Aufräumen.

lib/rdb.rb

@@ -3,6 +3,7 @@
 # A Ruby re-creation of /rdb, the relational database tools Mark Williams
 # Company sold for COHERENT (~1991).
 
+require 'bigdecimal'
 require 'open3'
 require 'date'
 require 'tmpdir'

lib/rdb/cmd/act.rb

@@ -8,12 +8,23 @@
 ACT_COMMANDS = %w[act adjust balance bom calcpay calculate cashflow chartdup close consolidate cstate explode
                   fillform foot getjournal invoice sale tax update.inv w2].freeze
 
+# Amounts are decimal numbers, not floats: sums of cents stay exact.
 def num(str)
-  str.to_s.strip.empty? ? 0.0 : str.to_s.strip.to_f
+  s = str.to_s.strip
+  s.match?(Rdb::NUM) ? BigDecimal(s.sub(/\.\z/, '')) : BigDecimal(s.to_f.to_s)
+end
+
+# Two decimals, always (money drops them from whole amounts).
+def fixed2(val)
+  val = BigDecimal(val.to_s) unless val.is_a?(BigDecimal)
+  val.round(2, :half_up).to_s('F').then { |t| t.sub(/\.(\d*)\z/) { ".#{Regexp.last_match(1).ljust(2, '0')}" } }
 end
 
 def money(val)
-  val == val.to_i ? val.to_i.to_s : format('%.2f', val)
+  val = BigDecimal(val.to_s) unless val.is_a?(BigDecimal)
+  return val.to_i.to_s if val == val.to_i
+
+  val.round(2, :half_up).to_s('F').sub(/\.(\d)\z/, '.\10')
 end
 
 def need(file)
@@ -73,7 +84,7 @@ Rdb.register('adjust', 'Create adjusted trial balance table', 'adjust') do |_arg
     m = (meta[h['Account']] ||= {})
     h.each { |k, v| m[k] = v if !v.to_s.strip.empty? && !%w[Debit Credit].include?(k) && !m.key?(k) }
   end
-  net = Hash.new(0.0)
+  net = Hash.new(BigDecimal(0))
   [tb, ja].each do |t|
     d = t.index_of('Debit')
     c = t.index_of('Credit')
@@ -135,7 +146,7 @@ Rdb.register('getjournal', 'Copy journals for sales, purchasing, pay systems', '
   a = t.index_of('Amount')
   total = t.rows.sum { |r| num(r[a]) }
   Rdb::Table.new(%w[Date Amount Account Ref Description],
-                 [[next_date, format('%.2f', total), '', t.rows.first&.fetch(t.head.index('Ref') || 0, ''), "#{args[0].delete_prefix('journal')} from #{args[0]}"]]).write
+                 [[next_date, fixed2(total), '', t.rows.first&.fetch(t.head.index('Ref') || 0, ''), "#{args[0].delete_prefix('journal')} from #{args[0]}"]]).write
 end
 
 Rdb.register('consolidate', 'Combine all subsidiary journals to general journal', 'consolidate nextdate') do |args|
@@ -172,7 +183,7 @@ Rdb.register('fillform', 'Fill a tax from with adjusted trial balance data', 'fi
   lines = need("taxform.#{args[0]}")
   trial = need('adjustedtrial')
   ti = trial.index_of('Taxline')
-  sums = Hash.new(0.0)
+  sums = Hash.new(BigDecimal(0))
   trial.rows.each { |r| sums[r[ti]] += (num(r[trial.index_of('Debit')]) - num(r[trial.index_of('Credit')])).abs }
   rows = lines.rows.map { |r| [r[0], money(sums[r[0]]), r[1].to_s] }
   File.write(args[0], Rdb::Table.new(%w[Taxline Amount Description], rows).to_s)
@@ -191,7 +202,7 @@ end
 
 Rdb.register('tax', 'Compute tax from income and tax table', 'tax income < taxtable') do |args|
   die 'usage: tax income < taxtable' unless args.size == 1
-  income = args[0].to_f
+  income = num(args[0])
   rows = table_in.rows.map { |r| r.map { |c| num(c) } }.sort_by(&:first)
   row = rows.reverse.find { |r| r[0] <= income }
   puts format('%7d', row ? (row[1] + (income - row[0]) * row[2] / 100.0).round : 0)
@@ -201,7 +212,7 @@ Rdb.register('cashflow', 'Compute balance column of cash table', 'cashflow < cas
   t = table_in
   a = t.index_of('Amount')
   b = t.index_of('Balance')
-  bal = 0.0
+  bal = BigDecimal(0)
   rows = t.rows.map do |r|
     r = r.dup
     if r[a].strip.empty? && !r[b].strip.empty?
@@ -239,9 +250,9 @@ end
 Rdb.register('bom', 'Produce bill-of-materials from parts list', 'bom') do |_args|
   part = need('part')
   items = need('saleitem')
-  qty = Hash.new(0.0)
+  qty = Hash.new(BigDecimal(0))
   items.rows.each { |r| qty[r[items.index_of('Code')]] += num(r[items.index_of('Qty')]) }
-  need_total = Hash.new(0.0)
+  need_total = Hash.new(BigDecimal(0))
   part.rows.each do |r|
     code = r[part.index_of('Code')]
     need_total[r[part.index_of('Subpart')]] += qty[code] * num(r[part.index_of('Count')]) if qty.key?(code)
@@ -252,8 +263,8 @@ end
 Rdb.register('explode', 'Produce table of subparts and their count for a part', 'explode Part Amount [ table ]') do |args|
   die 'usage: explode Part Amount [table]' if args.size < 2
   t = need(args[2] || 'parttable')
-  totals = Hash.new(0.0)
-  queue = [[args[0], args[1].to_f]]
+  totals = Hash.new(BigDecimal(0))
+  queue = [[args[0], num(args[1])]]
   until queue.empty?
     part, amount = queue.shift
     totals[part] += amount
@@ -298,9 +309,9 @@ Rdb.register('invoice', 'Print invoice for a sale order', 'invoice') do |_args|
     puts address_block(customers, oh['Cust'])
     mine = items.rows.select { |r| r[0] == n }
     items.with(rows: mine).write
-    puts format('%-40s Gross   %.2f', '', num(oh['Gross']))
-    puts format('%-40s Tax     %.2f', '', num(oh['Tax']))
-    puts format('%-40s Total   %.2f', '', num(oh['Total']))
+    puts format('%-40s Gross   %s', '', fixed2(num(oh['Gross'])))
+    puts format('%-40s Tax     %s', '', fixed2(num(oh['Tax'])))
+    puts format('%-40s Total   %s', '', fixed2(num(oh['Total'])))
   end
 end
 
@@ -314,15 +325,15 @@ Rdb.register('cstate', 'Produce customer statement', 'cstate') do |_args|
 
     chosen = c == 'all' ? orders.rows.map { |r| r[1] }.uniq : [c]
     chosen.each do |cust|
-      lines = orders.rows.select { |r| r[1] == cust }.map { |r| [cust, r[2], format('%.2f', -num(r[orders.index_of('Total')])), r[0]] } +
-              deposits.rows.select { |r| r[0] == cust }.map { |r| [cust, r[1], format('%.2f', num(r[2])), r[3]] }
+      lines = orders.rows.select { |r| r[1] == cust }.map { |r| [cust, r[2], fixed2(-num(r[orders.index_of('Total')])), r[0]] } +
+              deposits.rows.select { |r| r[0] == cust }.map { |r| [cust, r[1], fixed2(num(r[2])), r[3]] }
       balance = lines.sum { |l| num(l[2]) }
       puts '                Customer Statement', '                ------------------'
       puts address_block(customers, cust)
-      puts "Now Due and Payable is your balance of: #{format('%.2f', -balance)}"
+      puts "Now Due and Payable is your balance of: #{fixed2(-balance)}"
       puts 'Details of Your Orders and Payments'
       Rdb::Table.new(%w[Cust Date Amount Ref], lines.sort_by { |l| l[1] }).write
-      puts format('%-20s %s', '', format('%.2f', balance))
+      puts format('%-20s %s', '', fixed2(balance))
     end
   end
 end
@@ -348,7 +359,7 @@ Rdb.register('sale', 'Enter sale order, and item, update customer', 'sale') do |
     end
     puts address_block(customers, cust)
     n = Rdb::Table.open('salesorder').rows.map { |r| r[0].to_i }.max.to_i + 1
-    gross = 0.0
+    gross = BigDecimal(0)
     items = []
     loop do
       code = ask('Code (Return when done): ')
@@ -359,13 +370,13 @@ Rdb.register('sale', 'Enter sale order, and item, update customer', 'sale') do |
 
       q = ask('Qty: ').to_i
       price = num(p[products.index_of('Price')])
-      items << [n.to_s, (items.size + 1).to_s, code, '10', q.to_s, money(price), format('%.2f', price * q), p[products.index_of('Name')]]
+      items << [n.to_s, (items.size + 1).to_s, code, '10', q.to_s, money(price), fixed2(price * q), p[products.index_of('Name')]]
       gross += price * q
     end
     next if items.empty?
 
-    tax = gross * 0.05
-    order = [n.to_s, cust, next_date, '0', format('%.2f', gross), format('%.2f', tax), format('%.2f', gross + tax)]
+    tax = gross * BigDecimal('0.05')
+    order = [n.to_s, cust, next_date, '0', fixed2(gross), fixed2(tax), fixed2(gross + tax)]
     puts Rdb::Table.new(%w[Number Cust Date Shipped Gross Tax Total], [order]).to_s
     if ask('Is this correct? (y, n) ').downcase.start_with?('y')
       File.write('salesorder', Rdb::Table.open('salesorder').tap { |t| t.rows << order }.to_s)

lib/rdb/cmd/relational.rb

@@ -209,7 +209,7 @@ STATS.each do |cmd, desc|
     sel.each do |i|
       vals = t.rows.map { |r| r[i] }
       filled = vals.reject { |v| v.strip.empty? }
-      nums = filled.all? { |v| numeric?(v) } ? vals.map { |v| v.strip.to_f } : nil
+      nums = filled.all? { |v| numeric?(v) } ? vals.map { |v| v.strip.empty? ? BigDecimal(0) : dec_num(v) } : nil
       dec = filled.map { |v| decimals(v) }.max.to_i
       result[i] =
         case name
@@ -256,7 +256,7 @@ Rdb.register('subtotal', 'Output subtotals of columns in a table',
       vals = group.map { |r| r[i] }.reject { |v| v.strip.empty? }
       next if vals.empty? || !vals.all? { |v| numeric?(v) }
 
-      sub[i] = fmt(vals.sum { |v| v.strip.to_f }, vals.map { |v| decimals(v) }.max)
+      sub[i] = fmt(vals.sum { |v| dec_num(v) }, vals.map { |v| decimals(v) }.max)
     end
     if list
       out.concat(group)

lib/rdb/env.rb

@@ -30,8 +30,14 @@ module Rdb
       str.strip[/\.(\d+)\z/, 1].to_s.size
     end
 
+    # Decimal arithmetic, so that 0.1 + 0.2 is 0.3 and money adds up to the cent.
+    def dec_num(str)
+      BigDecimal(str.strip.sub(/\.\z/, ''))
+    end
+
     def fmt(num, dec)
-      dec.zero? ? num.round.to_s : format("%.#{dec}f", num)
+      num = BigDecimal(num.to_s) unless num.is_a?(BigDecimal)
+      dec.zero? ? num.round(0, :half_up).to_i.to_s : num.round(dec, :half_up).to_s('F').then { |t| t.sub(/\.(\d*)\z/) { ".#{Regexp.last_match(1).ljust(dec, '0')}" } }
     end
 
     def blank_row?(row)

lib/rdb/fast.rb

@@ -27,29 +27,39 @@ module Rdb
 
     Hit = Struct.new(:row, :xfrom, :xto)
 
-    # A table file read as bytes with the offset of every row.
+    # A table file. The head is read at once; the rows only when a method
+    # needs all of them (sequential search, -mb, update.rdb). A lookup through
+    # an index reads just its row, by byte offset.
     class Data
-      attr_reader :path, :head, :rows
+      attr_reader :path, :head
 
       def initialize(path)
         @path = path
         File.exist?(path) or Rdb.die("#{path}: no such table")
-        bytes = File.binread(path)
-        lines = []
-        off = 0
-        bytes.each_line("\n") do |l|
-          lines << Row.new(off, off + l.bytesize, l.chomp("\n"))
+        File.open(path, 'rb') do |f|
+          first = f.gets.to_s
+          Rdb.die("#{path}: is a list; fast access needs a table") if first == "\n"
+          @head = first.chomp("\n").split("\t", -1).map { |h| h.dup.force_encoding(Encoding::UTF_8).strip }
+          @body = f.pos
+          second = f.gets
+          @body = f.pos if second && Table.dash_line?(second.chomp("\n").split("\t", -1))
+        end
+      end
+
+      def rows
+        @rows ||= begin
+          bytes = File.binread(path).byteslice(@body..).to_s
+          off = @body
+          bytes.each_line("\n").map do |l|
+            row = Row.new(off, off + l.bytesize, l.chomp("\n"))
             off += l.bytesize
+            row
+          end
         end
-        Rdb.die("#{path}: is a list; fast access needs a table") if bytes.start_with?("\n")
-        @head = lines.shift&.line.to_s.split("\t", -1).map { |h| h.dup.force_encoding(Encoding::UTF_8).strip }
-        lines.shift if lines.first && Table.dash_line?(lines.first.cells)
-        @rows = lines
-        @by_from = lines.to_h { |r| [r.from, r] }
       end
 
       def live
-        @live ||= @rows.reject(&:blank?)
+        @live ||= rows.reject(&:blank?)
       end
 
       def column(name)
@@ -57,7 +67,14 @@ module Rdb
       end
 
       def row_at(offset)
-        @by_from[offset]
+        return @by_from[offset] if @rows && (@by_from ||= @rows.to_h { |r| [r.from, r] })
+        return nil if offset < @body
+
+        File.open(path, 'rb') do |f|
+          f.seek(offset)
+          line = f.gets or return nil
+          Row.new(offset, offset + line.bytesize, line.chomp("\n"))
+        end
       end
     end
 
@@ -80,8 +97,10 @@ module Rdb
       format("%8d\n", num)
     end
 
+    # FNV-1a over the key without blanks. (A plain sum of the bytes put
+    # 3000 five-digit numbers into 30 slots.)
     def hash_slot(slots, key)
-      key.delete(" \t").bytes.sum % slots
+      key.b.delete(" \t").each_byte.reduce(0xcbf29ce484222325) { |h, b| ((h ^ b) * 0x100000001b3) & 0xffffffffffffffff } % slots
     end
 
     def live_rows(data)
@@ -122,6 +141,56 @@ module Rdb
 
     # ---- searching ----------------------------------------------------------
 
+    # One entry of a fixed-width index (.r, .h) without reading the rest.
+    def fixed_count(path)
+      [(File.size(path) - FIXED_HEAD.bytesize) / ENTRY_WIDTH, 0].max
+    end
+
+    def fixed_entry(io, i)
+      io.seek(FIXED_HEAD.bytesize + ENTRY_WIDTH * i)
+      io.read(ENTRY_WIDTH).to_i
+    end
+
+    # Entries of an inverted index (.i) from the first key that is not below
+    # target, found by bisecting on byte positions. Yields hashes like
+    # read_inverted does.
+    def each_inverted_from(path, below)
+      File.open(path, 'rb') do |f|
+        f.gets
+        f.gets
+        lo = f.pos
+        hi = f.size
+        while lo < hi
+          mid = (lo + hi) / 2
+          if mid == lo
+            at = lo
+          else
+            f.seek(mid - 1)
+            f.gets
+            at = f.pos
+          end
+          if at >= hi
+            hi = mid
+            next
+          end
+          f.seek(at)
+          line = f.gets
+          if below.call(line.split("\t", 2)[0])
+            lo = at + line.bytesize
+          else
+            hi = at
+          end
+        end
+        f.seek(lo)
+        loop do
+          from = f.pos
+          line = f.gets or break
+          key, off = line.chomp("\n").split("\t", 2)
+          yield({ from: from, to: from + line.bytesize, key: key, offset: off.to_i })
+        end
+      end
+    end
+
     def read_fixed(path)
       File.binread(path).byteslice(FIXED_HEAD.bytesize..).to_s.lines.map { |l| l.to_i }
     end
@@ -166,29 +235,29 @@ module Rdb
           end
         end
       when 'r'
-        ents = read_fixed(path + '.r')
+        ip = path + '.r'
         n = keyvals[0].to_i
-        if n.positive? && n <= ents.size
-          r = data.row_at(ents[n - 1]) and hits << Hit.new(r, FIXED_HEAD.bytesize + ENTRY_WIDTH * (n - 1), FIXED_HEAD.bytesize + ENTRY_WIDTH * n)
+        if n.positive? && n <= fixed_count(ip)
+          off = File.open(ip, 'rb') { |f| fixed_entry(f, n - 1) }
+          r = data.row_at(off) and hits << Hit.new(r, FIXED_HEAD.bytesize + ENTRY_WIDTH * (n - 1), FIXED_HEAD.bytesize + ENTRY_WIDTH * n)
         end
       when 'i'
-        ents = read_inverted(path + '.i')
-        lo = ents.bsearch_index { |e| (partial ? norm(e[:key], true)[0, keyvals[0].strip.size] : e[:key].strip) >= (partial ? norm(keyvals[0], true) : keyvals[0].strip) }
-        if lo
-          ents[lo..].each do |e|
+        target = partial ? norm(keyvals[0], true) : keyvals[0].strip
+        below = ->(key) { (partial ? norm(key, true)[0, keyvals[0].strip.size] : key.strip) < target }
+        each_inverted_from(path + '.i', below) do |e|
           break unless matches?(e[:key], keyvals[0], partial, exact)
 
           r = data.row_at(e[:offset])
           hits << Hit.new(r, e[:from], e[:to]) if r
           break if first
         end
-        end
       when 'h'
-        ents = read_fixed(path + '.h')
-        slots = ents.size
+        ip = path + '.h'
+        slots = fixed_count(ip)
+        File.open(ip, 'rb') do |f|
           i = hash_slot(slots, keyvals[0])
           slots.times do
-          o = ents[i]
+            o = fixed_entry(f, i)
             break if o.zero?
 
             if o.positive? && (r = data.row_at(o)) && matches?(r.cells[idxs[0]], keyvals[0], false, exact)
@@ -197,6 +266,7 @@ module Rdb
             end
             i = (i + 1) % slots
           end
+        end
       else
         live_rows(data).each do |r|
           c = r.cells

test/rdb_test.rb

@@ -924,3 +924,40 @@ class RobustnessTest < RdbCase
     assert_empty Dir[File.join(@dir, 'wf.tmp*')]
   end
 end
+
+class ExactnessTest < RdbCase
+  def test_total_adds_decimals_exactly
+    out = rdb('total', 'A', stdin: "A\n-\n0.1\n0.2\n0.7\n0.3\n")
+    assert_equal '1.3', data(out).first.first
+  end
+
+  def test_mean_rounds_half_up
+    out = rdb('mean', 'A', stdin: "A\n-\n0.01\n0.02\n")
+    assert_equal '0.02', data(out).first.first
+  end
+
+  def test_subtotal_adds_decimals_exactly
+    out = rdb('subtotal', 'K', 'A', stdin: "K\tA\n-\t-\nx\t0.1\nx\t0.2\nx\t0.7\n")
+    assert_equal '1.0', data(out).first[1]
+  end
+
+  def test_hash_spreads_numeric_keys
+    slots = Hash.new(0)
+    (0...3000).each { |i| slots[Rdb::Fast.hash_slot(6000, format('%05d', i))] += 1 }
+    assert_operator slots.size, :>, 2000
+    assert_operator slots.values.max, :<=, 8
+  end
+
+  def test_indexed_search_does_not_read_all_rows
+    rows = (1..500).map { |i| "#{format('%04d', i)}\tv#{i}\n" }.join
+    write('big', "K\tV\n-\t-\n#{rows}")
+    %w[h i r].each { |m| rdb('index', "-m#{m}", 'big', 'K') }
+    data_obj = Rdb::Fast::Data.new(File.join(@dir, 'big'))
+    %w[h i].each do |m|
+      assert_equal ['0321', 'v321'], data(rdb('search', "-m#{m}", 'big', 'K', stdin: "0321\n")).first, "-m#{m}"
+    end
+    assert_equal ['0007', 'v7'], data(rdb('search', '-mr', 'big', stdin: "7\n")).first
+    assert_nil data_obj.instance_variable_get(:@rows)
+    assert_equal 'v500', data_obj.row_at(data_obj.rows.last.from).cells[1]
+  end
+end