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

Artifact a5e04b7a590f262c4100ba0b277387889802672b:


# 2008 May 12
#
# 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.
#
#***********************************************************************
#
# This file tests that if sqlite3_release_memory() is called to reclaim
# memory from a pager that is in the error-state, SQLite does not 
# incorrectly write dirty pages out to the database (not safe to do
# once the pager is in error state).
#
# $Id: ioerr5.test,v 1.5 2008/08/28 18:35:34 danielk1977 Exp $

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

ifcapable !memorymanage||!shared_cache {
  finish_test
  return
}

db close

set ::enable_shared_cache [sqlite3_enable_shared_cache 1]
set ::soft_limit [sqlite3_soft_heap_limit 1048576]

# This procedure prepares, steps and finalizes an SQL statement via the
# UTF-16 APIs. The text representation of an SQLite error code is returned
# ("SQLITE_OK", "SQLITE_IOERR" etc.). The actual results returned by the
# SQL statement, if it is a SELECT, are not available.
#
# This can be useful for testing because it forces SQLite to make an extra 
# call to sqlite3_malloc() when translating from the supplied UTF-16 to
# the UTF-8 encoding used internally.
#
proc dosql16 {zSql {db db}} {
  set sql [encoding convertto unicode $zSql]
  append sql "\00\00"
  set stmt [sqlite3_prepare16 $db $sql -1 {}]
  sqlite3_step $stmt
  set rc [sqlite3_finalize $stmt]
}

proc compilesql16 {zSql {db db}} {
  set sql [encoding convertto unicode $zSql]
  append sql "\00\00"
  set stmt [sqlite3_prepare16 $db $sql -1 {}]
  set rc [sqlite3_finalize $stmt]
}

# Open two database connections (handle db and db2) to database "test.db".
#
proc opendatabases {} {
  catch {db close}
  catch {db2 close}
  sqlite3 db test.db
  sqlite3 db2 test.db
  db2 cache size 0
  db cache size 0
  execsql {
    pragma page_size=512;
    pragma auto_vacuum=2;
    pragma cache_size=16;
  }
}

# Open two database connections and create a single table in the db.
#
do_test ioerr5-1.0 {
  opendatabases
  execsql { CREATE TABLE A(Id INTEGER, Name TEXT) }
} {}

foreach locking_mode {normal exclusive} {
  set nPage 2
  for {set iFail 1} {$iFail<200} {incr iFail} {
    sqlite3_soft_heap_limit 1048576
    opendatabases
    execsql { pragma locking_mode=exclusive }
    set nRow [db one {SELECT count(*) FROM a}]
  
    # Dirty (at least) one of the pages in the cache.
    do_test ioerr5-1.$locking_mode-$iFail.1 {
      execsql {
        BEGIN EXCLUSIVE;
        INSERT INTO a VALUES(1, 'ABCDEFGHIJKLMNOP');
      }
    } {}

    # Open a read-only cursor on table "a". If the COMMIT below is
    # interrupted by a persistent IO error, the pager will transition to 
    # PAGER_ERROR state. If there are no other read-only cursors open,
    # from there the pager immediately discards all cached data and 
    # switches to PAGER_OPEN state. This read-only cursor stops that
    # from happening, leaving the pager stuck in PAGER_ERROR state.
    #
    set channel [db incrblob -readonly a Name [db last_insert_rowid]]
  
    # Now try to commit the transaction. Cause an IO error to occur
    # within this operation, which moves the pager into the error state.
    #
    set ::sqlite_io_error_persist 1
    set ::sqlite_io_error_pending $iFail
    do_test ioerr5-1.$locking_mode-$iFail.2 {
      set rc [catchsql {COMMIT}]
      list
    } {}
    set ::sqlite_io_error_hit 0
    set ::sqlite_io_error_persist 0
    set ::sqlite_io_error_pending 0
  
    # Read the contents of the database file into a Tcl variable.
    #
    set fd [open test.db]
    fconfigure $fd -translation binary -encoding binary
    set zDatabase [read $fd]
    close $fd

    # Set a very low soft-limit and then try to compile an SQL statement 
    # from UTF-16 text. To do this, SQLite will need to reclaim memory
    # from the pager that is in error state. Including that associated
    # with the dirty page.
    #
    do_test ioerr5-1.$locking_mode-$iFail.3 {
      sqlite3_soft_heap_limit 1024
      compilesql16 "SELECT 10"
    } {}

    close $channel

    # Ensure that nothing was written to the database while reclaiming
    # memory from the pager in error state.
    #
    do_test ioerr5-1.$locking_mode-$iFail.4 {
      set fd [open test.db]
      fconfigure $fd -translation binary -encoding binary
      set zDatabase2 [read $fd]
      close $fd
      expr {$zDatabase eq $zDatabase2}
    } {1}

    if {$rc eq [list 0 {}]} {
      do_test ioerr5.1-$locking_mode-$iFail.3 {
        execsql { SELECT count(*) FROM a }
      } [expr $nRow+1]
      break
    }
  }
}

# Make sure this test script doesn't leave any files open.
#
do_test ioerr5-1.X {
  catch { db close }
  catch { db2 close }
  set sqlite_open_file_count
} 0

do_test ioerr5-2.0 {
  sqlite3 db test.db
  execsql { CREATE INDEX i1 ON a(id, name); }
} {}

foreach locking_mode {exclusive normal} {
  for {set iFail 1} {$iFail<200} {incr iFail} {
    sqlite3_soft_heap_limit 1048576
    opendatabases
    execsql { pragma locking_mode=exclusive }
    set nRow [db one {SELECT count(*) FROM a}]
  
    do_test ioerr5-2.$locking_mode-$iFail.1 {
      execsql {
        BEGIN EXCLUSIVE;
        INSERT INTO a VALUES(1, 'ABCDEFGHIJKLMNOP');
      }
    } {}

    set ::sqlite_io_error_persist 1
    set ::sqlite_io_error_pending $iFail

    sqlite3_release_memory 10000

    set error_hit $::sqlite_io_error_hit
    set ::sqlite_io_error_hit 0
    set ::sqlite_io_error_persist 0
    set ::sqlite_io_error_pending 0
    if {$error_hit} {
      do_test ioerr5-2.$locking_mode-$iFail.3a {
        catchsql COMMIT
      } {1 {disk I/O error}}
    } else {
      do_test ioerr5-2.$locking_mode-$iFail.3b {
        execsql COMMIT
      } {}
      break
    }
  }
}

# Make sure this test script doesn't leave any files open.
#
do_test ioerr5-2.X {
  catch { db close }
  catch { db2 close }
  set sqlite_open_file_count
} 0

sqlite3_enable_shared_cache $::enable_shared_cache
sqlite3_soft_heap_limit $::soft_limit

finish_test