Experimental change to the handling of foreign key constraint violations when applying a changeset: all foreign keys, immediate and deferred, are deferred until the end of the transaction (or sub-transaction) opened by the sqlite3changeset_apply(). A single call to the conflict-handler (if any) is made if any FK constraint violations are still present in the database at this point. The conflict-handler may choose to rollback the changeset, or to apply it, constraint violations and all.

FossilOrigin-Name: 1d44e5d3c2b1dc958442f9114a960b256e002ed3

src/sqliteInt.h

@@ -961,6 +961,7 @@ struct sqlite3 {
   int nSavepoint;               /* Number of non-transaction savepoints */
   int nStatement;               /* Number of nested statement-transactions  */
   i64 nDeferredCons;            /* Net deferred constraints this transaction. */
+  i64 nDeferredImmCons;         /* Net deferred immediate constraints */
   int *pnBytesFreed;            /* If not NULL, increment this in DbFree() */
 
 #ifdef SQLITE_ENABLE_UNLOCK_NOTIFY
@@ -1016,6 +1017,7 @@ struct sqlite3 {
 #define SQLITE_PreferBuiltin  0x00100000  /* Preference to built-in funcs */
 #define SQLITE_LoadExtension  0x00200000  /* Enable load_extension */
 #define SQLITE_EnableTrigger  0x00400000  /* True to enable triggers */
+#define SQLITE_DeferForeignKeys 0x00800000
 
 /*
 ** Bits of the sqlite3.dbOptFlags field that are used by the
@@ -1161,6 +1163,7 @@ struct FuncDestructor {
 struct Savepoint {
   char *zName;                        /* Savepoint name (nul-terminated) */
   i64 nDeferredCons;                  /* Number of deferred fk violations */
+  i64 nDeferredImmCons;               /* Number of deferred imm fk. */
   Savepoint *pNext;                   /* Parent savepoint (if any) */
 };