From: drh <drh@noemail.net>
Date: Thu, 26 Apr 2018 15:04:18 +0000 (+0000)
Subject: Clarification of the behavior of a BEFORE UPDATE trigger when the trigger
X-Git-Tag: version-3.24.0~89
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=de7ca50dac6a05b75ec4375116f1bcde8f19ded3;p=thirdparty%2Fsqlite.git

Clarification of the behavior of a BEFORE UPDATE trigger when the trigger
changes the values of some of the columns used to compute new columns in
the UPDATE.

FossilOrigin-Name: 7bb23c2a3d37f0d5e5515b917860818906819d54a0066e1ba8e9792a82f7d279
---

diff --git a/manifest b/manifest
index b7531d4c76..954f369eef 100644
--- a/manifest
+++ b/manifest
@@ -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
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F Makefile.in 5ce9343cba9c189046f1afe6d2bcc1f68079439febc05267b98aec6ecc752439
@@ -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
 F src/util.c d9eb0a6c4aae1b00a7369eadd7ca0bbe946cb4c953b6751aa20d357c2f482157
@@ -1477,7 +1477,7 @@ F test/trans.test 6e1b4c6a42dba31bd65f8fa5e61a2708e08ddde6
 F test/trans2.test 62bd045bfc7a1c14c5ba83ba64d21ade31583f76
 F test/trans3.test 91a100e5412b488e22a655fe423a14c26403ab94
 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
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P a956363cf6881be590120c7718976b54b12c4bd0d9228d8142b45e0fe1826f7e
-R 67e4930e9711eb625aa31c5083fa85ba
+P 368c14da868a843767344f6cc17c499fddd83244c0510337ed9a918e64ee2413
+R d67c07078741cec11cd337cb536cdcc8
 U drh
-Z bd6cee7c5fa35b400b9c5a8450cb9640
+Z aca21fa0a22205b706503004c2920563
diff --git a/manifest.uuid b/manifest.uuid
index 6175b6c3c8..1c442962fc 100644
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-368c14da868a843767344f6cc17c499fddd83244c0510337ed9a918e64ee2413
\ No newline at end of file
+7bb23c2a3d37f0d5e5515b917860818906819d54a0066e1ba8e9792a82f7d279
\ No newline at end of file
diff --git a/src/update.c b/src/update.c
index 80f3b43e86..dcab4eeb0b 100644
--- a/src/update.c
+++ b/src/update.c
@@ -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 ){
diff --git a/test/trigger1.test b/test/trigger1.test
index a190efd464..e785343b35 100644
--- a/test/trigger1.test
+++ b/test/trigger1.test
@@ -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