Fix some DROP CONSTRAINT and DROP NOT NULL cases involving SQL comments or multiple table constraints without separating commas.

FossilOrigin-Name: b0b02e58ac60e4371981938c904ccf831b2367e3fd7d22e0ec2b4782e4c6805b

manifest

@@ -1,5 +1,5 @@
-C Add\sfurther\stests\sfor\sthe\snew\sALTER\sTABLE\scommands\son\sthis\sbranch.
+C Fix\ssome\sDROP\sCONSTRAINT\sand\sDROP\sNOT\sNULL\scases\sinvolving\sSQL\scomments\sor\smultiple\stable\sconstraints\swithout\sseparating\scommas.
-D 2025-09-29T16:49:55.217
+D 2025-09-30T17:13:12.931
 F .fossil-settings/binary-glob 61195414528fb3ea9693577e1980230d78a1f8b0a54c78cf1b9b24d0a409ed6a x
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
@@ -670,7 +670,7 @@ F mptest/multiwrite01.test dab5c5f8f9534971efce679152c5146da265222d
 F sqlite.pc.in 42b7bf0d02e08b9e77734a47798d1a55a9e0716b
 F sqlite3.1 1b9c24374a85dfc7eb8fa7c4266ee0db4f9609cceecfc5481cd8307e5af04366
 F sqlite3.pc.in e6dee284fba59ef500092fdc1843df3be8433323a3733c91da96690a50a5b398
-F src/alter.c 875b85a0306968cfb811650d1c994bf65cf3112a521717d058e363705853a4a6
+F src/alter.c a2d3e4d1afe75c98048400b316e01c73a3688548ddbd9a8b76bebbae3f91b883
 F src/analyze.c 03bcfc083fc0cccaa9ded93604e1d4244ea245c17285d463ef6a60425fcb247d
 F src/attach.c 9af61b63b10ee702b1594ecd24fb8cea0839cfdb6addee52fba26fa879f5db9d
 F src/auth.c 54ab9c6c5803b47c0d45b76ce27eff22a03b4b1f767c5945a3a4eb13aa4c78dc
@@ -839,8 +839,8 @@ F test/alter4.test 37cafe164067a6590a0ee4cec780bddbbaa33dc50b11542dcfbe0e6562649
 F test/alterauth.test 63442ba61ceb0c1eeb63aac1f4f5cebfa509d352276059d27106ae256bafc959
 F test/alterauth2.test 4b74fa8f184f4736497317feb587b65759eb87d87acfe3a8ef433d4d18bb002b
 F test/altercol.test b43fb5725332f4cf8cff0280605202c1672e808281accea60a066d2ccc5129e5
-F test/altercons.test ac50608f34171021e67c5f2cbd9615a9fbf181804b84817d7a35e2cd89fbeb7d
+F test/altercons.test 22f4882404a7ba114ec9cbcadc4d15cea4a9ff73079d26cb649357808d586521
-F test/altercons2.test 9adc4e742655d2e55e38f507bd97dc1cd48bc91aa26b59bd3518fd2184a58114
+F test/altercons2.test 6e8e384f394ac1b6657429a885bc50be27bb88fe7427d8e1d5a64bdf600c221c
 F test/altercorrupt.test 2e1d705342cf9d7de884518ddbb053fd52d7e60d2b8869b7b63b2fda68435c12
 F test/alterdropcol.test a653a3945f964d26845ec0cd0a8e74189f46de3119a984c5bc45457da392612e
 F test/alterdropcol2.test 527fce683b200d620f560f666c44ae33e22728e990a10a48a543280dfd4b4d41
@@ -2171,8 +2171,8 @@ F tool/version-info.c 3b36468a90faf1bbd59c65fd0eb66522d9f941eedd364fabccd7227350
 F tool/warnings-clang.sh bbf6a1e685e534c92ec2bfba5b1745f34fb6f0bc2a362850723a9ee87c1b31a7
 F tool/warnings.sh 1ad0169b022b280bcaaf94a7fa231591be96b514230ab5c98fbf15cd7df842dd
 F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
-P 8f2e066e9a0a34fe7a41b153c0fb54b621128b2195141cc454a44180c969b4a9
+P 17a6f4e69e54a5dc233e33501f16f0f69f77fff071142cefc309b5407f57f721
-R 7160ac4e86f1b04a352a7675b4a73b19
+R cad1fca46ac4b09e84f0a86ca159c2b9
 U dan
-Z 729e8deb8af33990459f24e581d10a3d
+Z 5d912a204d4b04c238cd0328baa01045
 # Remove this line to create a well-formed Fossil manifest.

manifest.uuid

@@ -1 +1 @@
-17a6f4e69e54a5dc233e33501f16f0f69f77fff071142cefc309b5407f57f721
+b0b02e58ac60e4371981938c904ccf831b2367e3fd7d22e0ec2b4782e4c6805b

src/alter.c

@@ -2343,7 +2343,7 @@ static int getWhitespace(const u8 *z){
   while( 1 ){
     int t = 0;
     int n = sqlite3GetToken(&z[nRet], &t);
-    if( t!=TK_SPACE ) break;
+    if( t!=TK_SPACE && t!=TK_COMMENT ) break;
     nRet += n;
   }
   return nRet;
@@ -2361,7 +2361,7 @@ static int getConstraintToken(const u8 *z, int *piToken){
   int t = 0;
   do {
     iOff += sqlite3GetToken(&z[iOff], &t);
-  }while( t==TK_SPACE );
+  }while( t==TK_SPACE || t==TK_COMMENT );
 
   *piToken = t;
 
@@ -2386,8 +2386,8 @@ static int getConstraintToken(const u8 *z, int *piToken){
 
 /*
 ** Argument z points into the body of a constraint - specifically the 
-** token following the first of the 
+** second token of the constraint definition. Return the number of bytes
-** of bytes in string z to the end of the current constraint.
+** until the end of the constraint. 
 */
 static int getConstraint(const u8 *z){
   int iOff = 0;
@@ -2470,7 +2470,6 @@ static void dropConstraintFunc(
   int NotUsed,
   sqlite3_value **argv
 ){
-  const char *zSpace = " ";
   const u8 *zSql = sqlite3_value_text(argv[0]);
   const u8 *zCons = 0;
   int iNotNull = -1;
@@ -2496,8 +2495,8 @@ static void dropConstraintFunc(
     /* Now parse the column or table constraint definition. Search
     ** for the token CONSTRAINT if this is a DROP CONSTRAINT command, or
     ** NOT in the right column if this is a DROP NOT NULL. */
-    iStart = iOff - 1;
     while( 1 ){
+      iStart = iOff;
       iOff += getConstraintToken(&zSql[iOff], &t);
       if( t==TK_CONSTRAINT && (zCons || iNotNull==ii) ){
         /* Check if this is the constraint we are searching for. */
@@ -2515,9 +2514,26 @@ static void dropConstraintFunc(
         }
         iOff += nTok;
 
-        /* The first token of the constraint definition. */
+        /* The next token is usually the first token of the constraint
-        iOff += getConstraintToken(&zSql[iOff], &t);
+        ** definition. This is enough to tell the type of the constraint - 
-        iOff += getConstraint(&zSql[iOff]);
+        ** TK_NOT means it is a NOT NULL, TK_CHECK a CHECK constraint etc.
+        **
+        ** There is also the chance that the next token is TK_CONSTRAINT,
+        ** for example if a table has been created as follows:
+        **
+        **    CREATE TABLE t1(cols, CONSTRAINT one CONSTRAINT two NOT NULL);
+        **
+        ** In this case, allow the "CONSTRAINT one" bit to be dropped by
+        ** this command if that is what is requested, or to advance to
+        ** the next iteration of the loop with &zSql[iOff] still pointing
+        ** to the CONSTRAINT keyword.  */
+        nTok = getConstraintToken(&zSql[iOff], &t);
+        if( t==TK_CONSTRAINT || t==TK_COMMA || t==TK_RP ){
+          t = TK_CHECK;
+        }else{
+          iOff += nTok;
+          iOff += getConstraint(&zSql[iOff]);
+        }
 
         if( cmp==0 || (iNotNull>=0 && t==TK_NOT) ){
           if( t!=TK_NOT && t!=TK_CHECK ){
@@ -2537,7 +2553,6 @@ static void dropConstraintFunc(
       }else if( t==TK_COMMA ){
         break;
       }
-      iStart = iOff;
     }
   }
 
@@ -2551,10 +2566,16 @@ static void dropConstraintFunc(
       sqlite3_result_text(ctx, (const char*)zSql, -1, SQLITE_TRANSIENT);
     }
   }else{
-    /* Figure out if an extra space is required following the constraint. */
+
+    /* Figure out if an extra space should be inserted after the constraint
+    ** is removed. And if an additional comma preceding the constraint 
+    ** should be removed. */
+    const char *zSpace = " ";
+    iEnd += getWhitespace(&zSql[iEnd]);
     sqlite3GetToken(&zSql[iEnd], &t);
-    if( t==TK_RP || t==TK_SPACE || t==TK_COMMA ){
+    if( t==TK_RP || t==TK_COMMA ){
       zSpace = "";
+      if( zSql[iStart-1]==',' ) iStart--;
     }
 
     zNew = sqlite3_mprintf("%.*s%s%s", iStart, zSql, zSpace, &zSql[iEnd]);

test/altercons.test

@@ -57,6 +57,25 @@ foreach {tn before after} {
  11 { CREATE TABLE t1(a, b CONSTRAINT abc CHECK(t1.a != t1.b) REFERENCES t2) }
     { CREATE TABLE t1(a, b REFERENCES t2) }
 
+ 12 { CREATE TABLE t1(a, b, c, CONSTRAINT one CONSTRAINT abc CHECK(a!=b) CONSTRAINT three) }
+    { CREATE TABLE t1(a, b, c, CONSTRAINT one CONSTRAINT three) }
+
+ 13 { CREATE TABLE t1(a, b, c, CONSTRAINT abc CONSTRAINT one CHECK(a!=b) CONSTRAINT three) }
+    { CREATE TABLE t1(a, b, c, CONSTRAINT one CHECK(a!=b) CONSTRAINT three) }
+
+ 14 { CREATE TABLE t1(a, b, c, CONSTRAINT abc) }
+    { CREATE TABLE t1(a, b, c) }
+
+ 15 { CREATE TABLE t1(a, b, c,      
+                      CONSTRAINT abc, CHECK( a!=b )) }
+    { CREATE TABLE t1(a, b, c, CHECK( a!=b )) }
+
+ 16 { CREATE TABLE t1(a, b, c, CONSTRAINT abc /* hello */ CHECK( a!=b )) }
+    { CREATE TABLE t1(a, b, c) }
+
+ 17 { CREATE TABLE t1(a, b, c, /* world */ CONSTRAINT abc CHECK( a!=b )) }
+    { CREATE TABLE t1(a, b, c) }
+
 } {
   reset_db
 

test/altercons2.test

@@ -102,11 +102,37 @@ reset_db
 do_execsql_test 3.0 {
   CREATE TABLE t1(x);
 }
-
-breakpoint
 do_execsql_test 3.1 {
   ALTER TABLE t1 ALTER x SET NOT NULL;
 }
 
+#-------------------------------------------------------------------------
+reset_db
+do_execsql_test 4.0 {
+  CREATE TABLE abc(a, b, c, CONSTRAINT one CONSTRAINT two CHECK (b!=c));
+}
+do_execsql_test 4.1 {
+  ALTER TABLE abc DROP CONSTRAINT one
+}
+do_execsql_test 4.2 {
+  SELECT sql FROM sqlite_schema
+} {
+  {CREATE TABLE abc(a, b, c, CONSTRAINT two CHECK (b!=c))}
+}
+
+#-------------------------------------------------------------------------
+reset_db
+
+# The columns must come before the table constraints in a CREATE TABLE
+# statement. This is useful, as it means the DROP CONSTRAINT code does
+# not have to handle the constraint immediately following the '(' at
+# the start of the column-list.
+do_catchsql_test 5.0 {
+  CREATE TABLE abc(a, b, c, CONSTRAINT two CHECK (b!=c), d)
+} {1 {near "d": syntax error}}
+do_catchsql_test 5.1 {
+  CREATE TABLE def(CONSTRAINT abc CHECK( b!=c ), a, b, c);
+} {1 {near "CONSTRAINT": syntax error}}
+
 finish_test