SQLite中如何用触发器执行取消和重做逻辑--转?转载proc reload_all {} {? set body {}? foreach ns [names
SQLite中如何用触发器执行取消和重做逻辑--转
?
转载proc reload_all {} {
? set body {}
? foreach ns [namespace children ::] {
??? if {[info proc ${ns}::reload]==""} continue
??? append body ${ns}::reload\n
? }
? proc ::undo::reload_all {} $body
? reload_all
}
##############################################################################
# 这个模块的公共接口程序在上面。例行程序和变量静态追踪（名字以"_"开头的）是这个模块私有的。
##############################################################################
# state information
#
set _undo(active) 0
set _undo(undostack) {}
set _undo(redostack) {}
set _undo(pending) {}
set _undo(firstlog) 1
set _undo(startstate) {}
# proc:? ::undo::status_refresh
# title: Enable and/or disable menu options a buttons
#
proc status_refresh {} {
? variable _undo
? if {!$_undo(active) || [llength $_undo(undostack)]==0} {
??? .mb.edit entryconfig Undo -state disabled
??? .bb.undo config -state disabled
? } else {
??? .mb.edit entryconfig Undo -state normal
??? .bb.undo config -state normal
? }
? if {!$_undo(active) || [llength $_undo(redostack)]==0} {
??? .mb.edit entryconfig Redo -state disabled
??? .bb.redo config -state disabled
? } else {
??? .mb.edit entryconfig Redo -state normal
??? .bb.redo config -state normal
? }
}
# xproc:? ::undo::_create_triggers DB TABLE1 TABLE2 ...
# title:? Create change recording triggers for all tables listed
#
# 在数据库中创建一个名为"undolog"的临时表格。创建可以激发任何 insert, delete, or update of TABLE1, TABLE2, ....的触发器。
# 当这些触发器激发的时候，insert records in 在未做日志中插入记录，这些未做日志中包含SQL语句的文本，这些语句将撤销insert， delete，或update。
#
proc _create_triggers {db args} {
? catch {$db eval {DROP TABLE undolog}}
? $db eval {CREATE TEMP TABLE undolog(seq integer primary key, sql text)}
? foreach tbl $args {
??? set collist [$db eval "pragma table_info($tbl)"]
??? set sql "CREATE TEMP TRIGGER _${tbl}_it AFTER INSERT ON $tbl BEGIN\n"
??? append sql "? INSERT INTO undolog VALUES(NULL,"
??? append sql "'DELETE FROM $tbl WHERE rowid='||new.rowid);\nEND;\n"
??? append sql "CREATE TEMP TRIGGER _${tbl}_ut AFTER UPDATE ON $tbl BEGIN\n"
??? append sql "? INSERT INTO undolog VALUES(NULL,"
??? append sql "'UPDATE $tbl "
??? set sep "SET "
??? foreach {x1 name x2 x3 x4 x5} $collist {
????? append sql "$sep$name='||quote(old.$name)||'"
????? set sep ","
??? }
??? append sql " WHERE rowid='||old.rowid);\nEND;\n"
??? append sql "CREATE TEMP TRIGGER _${tbl}_dt BEFORE DELETE ON $tbl BEGIN\n"
??? append sql "? INSERT INTO undolog VALUES(NULL,"
??? append sql "'INSERT INTO ${tbl}(rowid"
??? foreach {x1 name x2 x3 x4 x5} $collist {append sql ,$name}
??? append sql ") VALUES('||old.rowid||'"
??? foreach {x1 name x2 x3 x4 x5} $collist {append sql ,'||quote(old.$name)||'}
??? append sql ")');\nEND;\n"
??? $db eval $sql
? }
}
# xproc:? ::undo::_drop_triggers DB
# title:? Drop all of the triggers that _create_triggers created
#
proc _drop_triggers {db} {
? set tlist [$db eval {SELECT name FROM sqlite_temp_master
?????????????????????? WHERE type='trigger'}]
? foreach trigger $tlist {
??? if {![regexp {^_.*_(i|u|d)t$} $trigger]} continue
??? $db eval "DROP TRIGGER $trigger;"
? }
? catch {$db eval {DROP TABLE undolog}}
}
# xproc: ::undo::_start_interval
# title: Record the starting conditions of an undo interval
#
proc _start_interval {} {
? variable _undo
? set _undo(firstlog) [db one {SELECT coalesce(max(seq),0)+1 FROM undolog}]
}
# xproc: ::undo::_step V1 V2
# title: Do a single step of undo or redo
#
# For an undo V1=="undostack" and V2=="redostack".? For a redo,
# V1=="redostack" and V2=="undostack".
#
proc _step {v1 v2} {
? variable _undo
? set op [lindex $_undo($v1) end]
? set _undo($v1) [lrange $_undo($v1) 0 end-1]
? foreach {begin end} $op break
? db eval BEGIN
? set q1 "SELECT sql FROM undolog WHERE seq>=$begin AND seq<=$end
????????? ORDER BY seq DESC"
? set sqllist [db eval $q1]
? db eval "DELETE FROM undolog WHERE seq>=$begin AND seq<=$end"
? set _undo(firstlog) [db one {SELECT coalesce(max(seq),0)+1 FROM undolog}]
? foreach sql $sqllist {
??? db eval $sql
? }
? db eval COMMIT
? reload_all
? set end [db one {SELECT coalesce(max(seq),0) FROM undolog}]
? set begin $_undo(firstlog)
? lappend _undo($v2) [list $begin $end]
? _start_interval
? refresh
}
# End of the ::undo namespace
}
