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SQLite training in Houston TX on 2019-11-05 (details)
Part of the 2019 Tcl Conference

Artifact be48f3a75eff0b4456209f26b3ce186c2015497d:


# 2015 Mar 17
#
# The author disclaims copyright to this source code.  In place of
# a legal notice, here is a blessing:
#
#    May you do good and not evil.
#    May you find forgiveness for yourself and forgive others.
#    May you share freely, never taking more than you give.
#
#***********************************************************************
#

set testdir [file dirname $argv0]
source $testdir/tester.tcl
source $testdir/lock_common.tcl
source $testdir/wal_common.tcl

finish_test; return;    #  Feature currently not implemented.
ifcapable !wal {finish_test ; return }
if {$::tcl_platform(platform)!="unix"} { finish_test ; return }
set testprefix walblock

catch { db close }
testvfs tvfs -fullshm 1
foreach f [glob test.db*] { forcedelete $f }

sqlite3 db test.db -vfs tvfs
do_execsql_test 1.1.0 {
  CREATE TABLE t1(x, y);
  INSERT INTO t1 VALUES(1, 2);
  INSERT INTO t1 VALUES(3, 4);
  INSERT INTO t1 VALUES(5, 6);
  PRAGMA journal_mode = wal;
  INSERT INTO t1 VALUES(7, 8);
} {wal}

do_test 1.1.1 { 
  lsort [glob test.db*] 
} {test.db test.db-shm test.db-wal}

do_test 1.1.2 { 
  set C [launch_testfixture]
  testfixture $C {
    sqlite3 db test.db
    db eval { SELECT * FROM t1 }
  }
} {1 2 3 4 5 6 7 8}

do_test 1.1.3 { 
  set ::out [list]
  testfixture $C {
    db eval { SELECT * FROM t1 }
  } [list set ::out]
  set ::out
} {}

do_test 1.1.4 { 
  vwait ::out
  set ::out
} {1 2 3 4 5 6 7 8}

#
# Test that if a read client cannot read the wal-index header because a
# write client is in the middle of updating it, the reader blocks until
# the writer finishes.
#
#   1. Open a write transaction using client [db] in this process.
#
#   2. Attempt to commit the write transaction. Intercept the xShmBarrier()
#      call made by the writer between updating the two copies of the
#      wal-index header.
#
#   3. Within the xShmBarrier() callback, make an asynchronous request to
#      the other process to read from the database. It should block, as it
#      cannot get read the wal-index header.
#
#   4. Still in xShmBarrier(), wait for 5 seconds. Check that the other
#      process has not answered the request.
#
#   5: Finish committing the transaction. Then wait for 0.5 seconds more.
#      Ensure that the second process has by this stage read the database
#      and that the snapshot it read included the transaction committed in
#      step (4).
#
do_execsql_test 1.2.1 {
  BEGIN;
    INSERT INTO t1 VALUES(9, 10);
} {}

tvfs script barrier_callback
tvfs filter xShmBarrier
proc barrier_callback {method args} {
  set ::out ""
  testfixture $::C { db eval { SELECT * FROM t1 } } {set ::out}

  do_test "1.2.2.(blocking 10 seconds)" { 
    set ::continue 0
    after 10000 {set ::continue 1}
    vwait ::continue
    set ::out 
  } {}
}

execsql COMMIT

do_test "1.2.3.(blocking 0.5 seconds)" { 
  set ::continue 0
  after 500 {set ::continue 1}
  vwait ::continue
  set ::out 
} {1 2 3 4 5 6 7 8 9 10}


finish_test