Illustration of sqlite3 3.26.0 test case "btree02-110" regression (fixed in current sqlite3-trunk)

## Sqlite3 test case btree02-110 wrapped to illustrates check-in
## https://www2.sqlite.org/src/fdiff?v1=a0f33669ba766322&v2=7555a5440453d900
##
## Variant "new, amend +160" is the current state of trunk (sqlite3-repo).

## ================= 8.6.8 ===================
## old, amend
##   ==> 20 ==? 27 (expected)
## new, amend
##   ==> 10 ==? 10 (expected)
## old, amend +160
##   ==> 20 ==? 27 (expected)
## new, amend +160
##   ==> 10 ==? 10 (expected)
##   
## ================= 8.6.9.1 ===================
## old, amend
##   ==> 27 ==? 27 (expected)
## new, amend
##   ==> 24 ==? 10 (expected)
## old, amend +160
##   ==> 20 ==? 27 (expected)
## new, amend +160
##   ==> 10 ==? 10 (expected)
## 
## ================= 8.5 (latest) ===================
## old, amend
##   ==> 27 ==? 27 (expected)
## new, amend
##   ==> 24 ==? 10 (expected)
## old, amend +160
##   ==> 20 ==? 27 (expected)
## new, amend +160
##   ==> 10 ==? 10 (expected)

## =============================================================================

proc _init {{amend {}}} {
  catch {db close}
  sqlite3 db :memory:
  db eval "
    CREATE TABLE t1(a TEXT, ax INTEGER, b INT, PRIMARY KEY(a,ax)) WITHOUT ROWID;
    WITH RECURSIVE c(i) AS (VALUES(1) UNION ALL SELECT i+1 FROM c WHERE i<10)
      INSERT INTO t1(a,ax,b) SELECT printf('%02x',i$amend), random(), i FROM c;
    CREATE INDEX t1a ON t1(a);
    CREATE TABLE t2(x,y);
    CREATE TABLE t3(cnt);
    WITH RECURSIVE c(i) AS (VALUES(1) UNION ALL SELECT i+1 FROM c WHERE i<4)
      INSERT INTO t3(cnt) SELECT i FROM c;
    SELECT count(*) FROM t1;
  "
}

foreach amend {{} +160} {
  ## old (3.26.0) test-case [3f5f60cd75]:
  puts "old, amend $amend"
  _init $amend

  puts "  ==> [eval {
    db eval BEGIN
    set i 0
    db eval {SELECT a, ax, b, cnt FROM t1 CROSS JOIN t3 WHERE b IS NOT NULL} {
      if {$a==""} {set a 0}
      if {$b==""} {set b 0}    
      db eval {INSERT INTO t2(x,y) VALUES($b,$cnt)}
      # puts "a,b,cnt = ($a,$b,$cnt)"
      incr i
      if {$i%2==1} {
        set bx [expr {$b+1000}]
        # puts "INSERT ($a),$bx"
        db eval {INSERT INTO t1(a,ax,b) VALUES(printf('(%s)',$a),random(),$bx)}

      } else {
        # puts "DELETE a=$a"
        db eval {DELETE FROM t1 WHERE a=$a}

      }
      db eval {COMMIT; BEGIN}
    }  
    db one {COMMIT; SELECT count(*) FROM t1;}
  }] ==? 27 (expected)"
  db close

  ## new fixed test-case [d9e4f95746] at 2018-12-27 16:55:01 on branch trunk:
  puts "new, amend $amend"
  _init $amend

  puts "  ==> [eval {
    db eval BEGIN
    set i 0
    # showt1
    db eval {SELECT a, ax, b, cnt FROM t1 CROSS JOIN t3 WHERE b IS NOT NULL} {
      if {$a==""} continue
      db eval {INSERT INTO t2(x,y) VALUES($b,$cnt)}
      # puts "a,b,cnt = ($a,$b,$cnt)"
      incr i
      if {$i%2==1} {
        set bx [expr {$b+1000}]
        #  puts "INSERT ($a),$bx"
        db eval {INSERT INTO t1(a,ax,b) VALUES(printf('(%s)',$a),random(),$bx)}
        # showt1
      } else {
        # puts "DELETE a=$a"
        db eval {DELETE FROM t1 WHERE a=$a}
        # showt1
      }
      db eval {COMMIT; BEGIN}
    }  
    db one {COMMIT; SELECT count(*) FROM t1;}
  }] ==? 10 (expected)"
  db close
}