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Clarification of the behavior of a BEFORE UPDATE trigger when the trigger

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changes the values of some of the columns used to compute new columns in
the UPDATE.

FossilOrigin-Name: 7bb23c2a3d37f0d5e5515b917860818906819d54a0066e1ba8e9792a82f7d279
This commit is contained in:
drh 2018-04-26 15:04:18 +00:00
parent 896494e8ad
commit de7ca50dac
4 changed files with 37 additions and 11 deletions
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14
manifest
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@ -1,5 +1,5 @@
C Improved\sVDBE\scomment\son\sthe\sOP_Param\sopcode.\s\sNo\ssubstantial\schanges.
D 2018-04-26T12:27:03.691
C Clarification\sof\sthe\sbehavior\sof\sa\sBEFORE\sUPDATE\strigger\swhen\sthe\strigger\nchanges\sthe\svalues\sof\ssome\sof\sthe\scolumns\sused\sto\scompute\snew\scolumns\sin\nthe\sUPDATE.
D 2018-04-26T15:04:18.138
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@ -557,7 +557,7 @@ F src/threads.c 4ae07fa022a3dc7c5beb373cf744a85d3c5c6c3c
F src/tokenize.c bbde32eac9eb1280f5292bcdfef66f5a57e43176cbf9347e0efab9f75e133f97
F src/treeview.c 6cea286ca9af8b126dae9714799265353387244eba0d451c3cc2cd60946cc4c7
F src/trigger.c 4ace6d1d5ba9a89822deb287317f33c810440526eafe185c2d8a48c31df1e995
F src/update.c 0d53281948be1c7f7242151fe9adcdcb02eb9faeb1ee4c98cffd67c12adc3599
F src/update.c 2946cf3c6995f9d5cdccedcc08339d18b8eae72c15f06c011ef3230550c0583b
F src/upsert.c ae4a4823b45c4daf87e8aea8c0f582a8844763271f5ed54ee5956c4c612734f4
F src/utf.c 810fbfebe12359f10bc2a011520a6e10879ab2a163bcb26c74768eab82ea62a5
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@ -1477,7 +1477,7 @@ F test/trans.test 6e1b4c6a42dba31bd65f8fa5e61a2708e08ddde6
F test/trans2.test 62bd045bfc7a1c14c5ba83ba64d21ade31583f76
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F test/transitive1.test 293300f46916569f08875cdb2fe2134be2c27677
F test/trigger1.test ea9624cc1dae05645469df6119fa815f9e6f1e8c
F test/trigger1.test d7bdbff72c65293dddc8a443c3fd90b957869ac274c5e25ea6acc326f5e3c233
F test/trigger2.test 5cd7d69a7ba1143ee045e4ae2963ff32ae4c87a6
F test/trigger3.test aa640bb2bbb03edd5ff69c055117ea088f121945
F test/trigger4.test 74700b76ebf3947b2f7a92405141eb2cf2a5d359
@ -1725,7 +1725,7 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
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@ -1 +1 @@
368c14da868a843767344f6cc17c499fddd83244c0510337ed9a918e64ee2413
7bb23c2a3d37f0d5e5515b917860818906819d54a0066e1ba8e9792a82f7d279

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src/update.c
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@ -639,10 +639,13 @@ void sqlite3Update(
VdbeCoverage(v);
}
/* If it did not delete it, the row-trigger may still have modified
/* If it did not delete it, the BEFORE trigger may still have modified
** some of the columns of the row being updated. Load the values for
** all columns not modified by the update statement into their
** registers in case this has happened.
** all columns not modified by the update statement into their registers
** in case this has happened. Only unmodified columns are reloaded.
** The values computed for modified columns use the values before the
** BEFORE trigger runs. See test case trigger1-18.0 (added 2018-04-26)
** for an example.
*/
for(i=0; i<pTab->nCol; i++){
if( aXRef[i]<0 && i!=pTab->iPKey ){

23
test/trigger1.test
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@ -728,4 +728,27 @@ do_execsql_test trigger1-17.0 {
PRAGMA integrity_check;
} {ok}
# 2018-04-26
# When a BEFORE UPDATE trigger changes a column value in a row being
# updated, and that column value is used by the UPDATE to change other
# column, the value used to compute the update is from before the trigger.
# In the example that follows, the value of "b" in "c=b" is 2 (the value
# prior to running the BEFORE UPDATE trigger) not 1000.
#
do_execsql_test trigger1-18.0 {
CREATE TABLE t18(a PRIMARY KEY,b,c);
INSERT INTO t18(a,b,c) VALUES(1,2,3);
CREATE TRIGGER t18r1 BEFORE UPDATE ON t18 BEGIN
UPDATE t18 SET b=1000 WHERE a=old.a;
END;
UPDATE t18 SET c=b WHERE a=1;
SELECT * FROM t18;
} {1 1000 2} ;# Not: 1 1000 1000
do_execsql_test trigger1-18.1 {
DELETE FROM t18;
INSERT INTO t18(a,b,c) VALUES(1,2,3);
UPDATE t18 SET c=b, b=b+1 WHERE a=1;
SELECT * FROM t18;
} {1 3 2} ;# Not: 1 1001 1000
finish_test