perf: 50K benchmark — Harbour vs Five on ext4

50K records benchmark on native ext4 (home directory):
- APPEND 50K: Five 140ms / Harbour 61ms (2.3x)
- INDEX 50K:  Five 31ms / Harbour 6ms (5.2x)
- SEEK 50K:   Five 142ms / Harbour 23ms (6.2x)
- SCAN 50K:   Five 35ms / Harbour 5ms (7x)
- PACK 50K:   Five 19ms / Harbour 16ms (1.2x)

All within acceptable Go vs C overhead (2-7x).
PACK nearly identical. APPEND close (2.3x).

Known issue: 3-level NTX bulk build has separator duplication
at interior→root level (count=50083 vs 50000).
Does not affect correctness for <= 2-level trees (100 records OK).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

examples/bench_heavy.prg

@@ -0,0 +1,174 @@
+// Heavy RDD benchmark — 50K records, multiple indexes, mixed operations
+
+
+PROCEDURE Main()
+   LOCAL i, j, nH, nStart, nEnd, nCount, nSum
+   LOCAL aStruct, aCities, nIdx
+
+   ErrorBlock({|e| Break(e)})
+   aCities := {"Seoul","Tokyo","Beijing","London","NYC","Paris","Berlin","Rome","Madrid","Oslo"}
+
+   aStruct := { ;
+      {"ID","N",8,0}, {"NAME","C",30,0}, {"CITY","C",15,0}, ;
+      {"SALARY","N",12,2}, {"ACTIVE","L",1,0}, {"CODE","C",10,0} ;
+   }
+
+   BEGIN SEQUENCE
+
+   // ======== APPEND 50K ========
+   nStart := Seconds()
+   dbCreate("heavy_test", aStruct)
+   USE "heavy_test" NEW
+   FOR i := 1 TO 50000
+      APPEND BLANK
+      REPLACE ID     WITH i
+      REPLACE NAME   WITH PadR("Name_" + PadL(LTrim(Str(i)), 5, "0"), 30)
+      nIdx := ((i-1) % 10) + 1
+      REPLACE CITY   WITH PadR(aCities[nIdx], 15)
+      REPLACE SALARY WITH 20000 + i * 1.50
+      REPLACE ACTIVE WITH (i % 3 != 0)
+      REPLACE CODE   WITH PadR(LTrim(Str(Int(((i-1)/500))+1)), 10)
+   NEXT
+   nEnd := Seconds()
+   R("H1_APPEND_50K", FmtMs(nEnd - nStart) + " rc=" + LTrim(Str(RecCount())))
+
+   // ======== INDEX 50K ========
+   nStart := Seconds()
+   INDEX ON FIELD->NAME TO heavy_name
+   nEnd := Seconds()
+   R("H2_INDEX_50K", FmtMs(nEnd - nStart))
+   CLOSE ALL
+
+   // ======== SEEK 50K sequential ========
+   USE "heavy_test" NEW
+   SET INDEX TO heavy_name
+   nStart := Seconds()
+   nCount := 0
+   FOR i := 1 TO 50000
+      SEEK PadR("Name_" + PadL(LTrim(Str(i)), 5, "0"), 30)
+      IF Found()
+         nCount++
+      ENDIF
+   NEXT
+   nEnd := Seconds()
+   R("H3_SEEK_50K", FmtMs(nEnd - nStart) + " f=" + LTrim(Str(nCount)))
+
+   // ======== SEEK 50K random ========
+   nStart := Seconds()
+   nCount := 0
+   FOR i := 1 TO 50000
+      j := ((i * 7919) % 50000) + 1
+      SEEK PadR("Name_" + PadL(LTrim(Str(j)), 5, "0"), 30)
+      IF Found()
+         nCount++
+      ENDIF
+   NEXT
+   nEnd := Seconds()
+   R("H4_SEEK_RND", FmtMs(nEnd - nStart) + " f=" + LTrim(Str(nCount)))
+   CLOSE ALL
+
+   // ======== FULL SCAN 50K ========
+   USE "heavy_test" NEW
+   SET INDEX TO heavy_name
+   nStart := Seconds()
+   GO TOP
+   nCount := 0
+   DO WHILE !EOF()
+      nCount++
+      SKIP
+   ENDDO
+   nEnd := Seconds()
+   R("H5_SCAN_50K", FmtMs(nEnd - nStart) + " c=" + LTrim(Str(nCount)))
+   CLOSE ALL
+
+   // ======== CITY INDEX 50K ========
+   USE "heavy_test" NEW
+   nStart := Seconds()
+   INDEX ON FIELD->CITY TO heavy_city
+   nEnd := Seconds()
+   R("H6_IDX_CITY", FmtMs(nEnd - nStart))
+
+   // ======== DUP KEY SEEK+SCAN ========
+   nStart := Seconds()
+   nCount := 0
+   FOR i := 1 TO 10
+      SEEK PadR(aCities[i], 15)
+      DO WHILE !EOF() .AND. RTrim(FieldGet(3)) == aCities[i]
+         nCount++
+         SKIP
+      ENDDO
+   NEXT
+   nEnd := Seconds()
+   R("H7_DUPKEY_50K", FmtMs(nEnd - nStart) + " c=" + LTrim(Str(nCount)))
+   CLOSE ALL
+
+   // ======== DELETE 10K + SET DELETED SCAN ========
+   USE "heavy_test" NEW
+   SET INDEX TO heavy_name
+   SET ORDER TO 0
+   FOR i := 1 TO 50000
+      GO i
+      IF i % 5 == 0
+         DELETE
+      ENDIF
+   NEXT
+
+   SET ORDER TO 1
+   SET DELETED ON
+   nStart := Seconds()
+   GO TOP
+   nCount := 0
+   DO WHILE !EOF()
+      nCount++
+      SKIP
+   ENDDO
+   nEnd := Seconds()
+   R("H8_DELSCAN_50K", FmtMs(nEnd - nStart) + " c=" + LTrim(Str(nCount)))
+
+   SET DELETED OFF
+   SET ORDER TO 0
+   FOR i := 1 TO 50000
+      GO i
+      IF Deleted()
+         RECALL
+      ENDIF
+   NEXT
+   CLOSE ALL
+
+   // ======== COMPOUND INDEX ========
+   USE "heavy_test" NEW
+   nStart := Seconds()
+   INDEX ON FIELD->CITY + FIELD->NAME TO heavy_comp
+   nEnd := Seconds()
+   R("H9_IDX_COMP", FmtMs(nEnd - nStart))
+
+   SEEK PadR("Seoul", 15) + PadR("Name_00001", 30)
+   R("H10_COMP_SEEK", IIF(Found(),".T.",".F.") + " " + LTrim(Str(RecNo())))
+   CLOSE ALL
+
+   // ======== PACK 50K (10K deleted) ========
+   USE "heavy_test" NEW
+   FOR i := 1 TO 50000
+      GO i
+      IF i % 5 == 0
+         DELETE
+      ENDIF
+   NEXT
+   nStart := Seconds()
+   PACK
+   nEnd := Seconds()
+   R("H11_PACK_50K", FmtMs(nEnd - nStart) + " rc=" + LTrim(Str(RecCount())))
+   CLOSE ALL
+
+   RECOVER
+      ? "ERROR"
+   END SEQUENCE
+
+RETURN
+
+FUNCTION FmtMs(nSec)
+RETURN LTrim(Str(Int(nSec * 1000))) + "ms"
+
+PROCEDURE R(cKey, cVal)
+   ? cKey + "=" + cVal
+RETURN