Fix the DROP TABLE command so that it cannot be used to bypass foreign key constraints (if foreign key support is enabled).
FossilOrigin-Name: 8353808c9e70412fdee31bfda7810e948f1c7485
diff --git a/src/build.c b/src/build.c
index 544014d..215b3c0 100644
--- a/src/build.c
+++ b/src/build.c
@@ -2061,6 +2061,7 @@
sqlite3VdbeAddOp0(v, OP_VBegin);
}
#endif
+ sqlite3FkDropTable(pParse, pName, pTab);
/* Drop all triggers associated with the table being dropped. Code
** is generated to remove entries from sqlite_master and/or
diff --git a/src/fkey.c b/src/fkey.c
index 804d1ed..706e054 100644
--- a/src/fkey.c
+++ b/src/fkey.c
@@ -588,6 +588,64 @@
}
/*
+** This function is called to generate code that runs when table pTab is
+** being dropped from the database. The SrcList passed as the second argument
+** to this function contains a single entry guaranteed to resolve to
+** table pTab.
+**
+** Normally, no code is required. However, if either
+**
+** (a) The table is the parent table of a FK constraint, or
+** (b) The table is the child table of a deferred FK constraint and it is
+** determined at runtime that there are outstanding deferred FK
+** constraint violations in the database,
+**
+** then the equivalent of "DELETE FROM <tbl>" is executed before dropping
+** the table from the database. Triggers are disabled while running this
+** DELETE, but foreign key actions are not.
+*/
+void sqlite3FkDropTable(Parse *pParse, SrcList *pName, Table *pTab){
+ sqlite3 *db = pParse->db;
+ if( (db->flags&SQLITE_ForeignKeys) && !IsVirtual(pTab) && !pTab->pSelect ){
+ int iSkip = 0;
+ Vdbe *v = sqlite3GetVdbe(pParse);
+
+ assert( v ); /* VDBE has already been allocated */
+ if( sqlite3FkReferences(pTab)==0 ){
+ /* Search for a deferred foreign key constraint for which this table
+ ** is the child table. If one cannot be found, return without
+ ** generating any VDBE code. If one can be found, then jump over
+ ** the entire DELETE if there are no outstanding deferred constraints
+ ** when this statement is run. */
+ FKey *p;
+ for(p=pTab->pFKey; p; p=p->pNextFrom){
+ if( p->isDeferred ) break;
+ }
+ if( !p ) return;
+ iSkip = sqlite3VdbeMakeLabel(v);
+ sqlite3VdbeAddOp2(v, OP_FkIfZero, 1, iSkip);
+ }
+
+ pParse->disableTriggers = 1;
+ sqlite3DeleteFrom(pParse, sqlite3SrcListDup(db, pName, 0), 0);
+ pParse->disableTriggers = 0;
+
+ /* If the DELETE has generated immediate foreign key constraint
+ ** violations, halt the VDBE and return an error at this point, before
+ ** any modifications to the schema are made. This is because statement
+ ** transactions are not able to rollback schema changes. */
+ sqlite3VdbeAddOp2(v, OP_FkIfZero, 0, sqlite3VdbeCurrentAddr(v)+2);
+ sqlite3HaltConstraint(
+ pParse, OE_Abort, "foreign key constraint failed", P4_STATIC
+ );
+
+ if( iSkip ){
+ sqlite3VdbeResolveLabel(v, iSkip);
+ }
+ }
+}
+
+/*
** This function is called when inserting, deleting or updating a row of
** table pTab to generate VDBE code to perform foreign key constraint
** processing for the operation.
diff --git a/src/sqliteInt.h b/src/sqliteInt.h
index 60414f7..2ae1ec8 100644
--- a/src/sqliteInt.h
+++ b/src/sqliteInt.h
@@ -2122,6 +2122,7 @@
u32 oldmask; /* Mask of old.* columns referenced */
u8 eTriggerOp; /* TK_UPDATE, TK_INSERT or TK_DELETE */
u8 eOrconf; /* Default ON CONFLICT policy for trigger steps */
+ u8 disableTriggers; /* True to disable triggers */
/* Above is constant between recursions. Below is reset before and after
** each recursion */
@@ -2949,15 +2950,17 @@
*/
#if !defined(SQLITE_OMIT_FOREIGN_KEY) && !defined(SQLITE_OMIT_TRIGGER)
void sqlite3FkCheck(Parse*, Table*, ExprList*, int, int);
+ void sqlite3FkDropTable(Parse*, SrcList *, Table*);
void sqlite3FkActions(Parse*, Table*, ExprList*, int);
int sqlite3FkRequired(Parse*, Table*, ExprList*);
u32 sqlite3FkOldmask(Parse*, Table*, ExprList*);
FKey *sqlite3FkReferences(Table *);
#else
- #define sqlite3FkCheck(a,b,c,d,e)
#define sqlite3FkActions(a,b,c,d)
- #define sqlite3FkRequired(a,b,c) 0
+ #define sqlite3FkCheck(a,b,c,d,e)
+ #define sqlite3FkDropTable(a,b,c)
#define sqlite3FkOldmask(a,b,c) 0
+ #define sqlite3FkRequired(a,b,c) 0
#endif
#ifndef SQLITE_OMIT_FOREIGN_KEY
void sqlite3FkDelete(Table*);
diff --git a/src/trigger.c b/src/trigger.c
index dfe8e9a..319f9bc 100644
--- a/src/trigger.c
+++ b/src/trigger.c
@@ -50,6 +50,10 @@
Schema * const pTmpSchema = pParse->db->aDb[1].pSchema;
Trigger *pList = 0; /* List of triggers to return */
+ if( pParse->disableTriggers ){
+ return 0;
+ }
+
if( pTmpSchema!=pTab->pSchema ){
HashElem *p;
for(p=sqliteHashFirst(&pTmpSchema->trigHash); p; p=sqliteHashNext(p)){