https://sqlite.org/forum/forumpost/cb59d962fd
https://sqlite.org/src/vinfo/d8c6b246
https://sqlite.org/src/info/67da596d82ec0ed3 (backport)

--- a/ext/fts5/fts5_index.c
+++ b/ext/fts5/fts5_index.c
@@ -355,10 +355,11 @@
   int nContentlessDelete;         /* Number of contentless delete ops */
   int nPendingRow;                /* Number of INSERT in hash table */
 
   /* Error state. */
   int rc;                         /* Current error code */
+  int flushRc;
 
   /* State used by the fts5DataXXX() functions. */
   sqlite3_blob *pReader;          /* RO incr-blob open on %_data table */
   sqlite3_stmt *pWriter;          /* "INSERT ... %_data VALUES(?,?)" */
   sqlite3_stmt *pDeleter;         /* "DELETE FROM %_data ... id>=? AND id<=?" */
@@ -4000,10 +4001,11 @@
   assert( p->pHash || p->nPendingData==0 );
   if( p->pHash ){
     sqlite3Fts5HashClear(p->pHash);
     p->nPendingData = 0;
     p->nPendingRow = 0;
+    p->flushRc = SQLITE_OK;
   }
   p->nContentlessDelete = 0;
 }
 
 /*
@@ -5582,18 +5584,24 @@
 /*
 ** Flush any data stored in the in-memory hash tables to the database.
 */
 static void fts5IndexFlush(Fts5Index *p){
   /* Unless it is empty, flush the hash table to disk */
+  if( p->flushRc ){
+    p->rc = p->flushRc;
+    return;
+  }
   if( p->nPendingData || p->nContentlessDelete ){
     assert( p->pHash );
     fts5FlushOneHash(p);
     if( p->rc==SQLITE_OK ){
       sqlite3Fts5HashClear(p->pHash);
       p->nPendingData = 0;
       p->nPendingRow = 0;
       p->nContentlessDelete = 0;
+    }else if( p->nPendingData || p->nContentlessDelete ){
+      p->flushRc = p->rc;
     }
   }
 }
 
 static Fts5Structure *fts5IndexOptimizeStruct(

--- a/ext/fts5/fts5_main.c
+++ b/ext/fts5/fts5_main.c
@@ -116,11 +116,11 @@
   Fts5Table p;                    /* Public class members from fts5Int.h */
   Fts5Storage *pStorage;          /* Document store */
   Fts5Global *pGlobal;            /* Global (connection wide) data */
   Fts5Cursor *pSortCsr;           /* Sort data from this cursor */
   int iSavepoint;                 /* Successful xSavepoint()+1 */
-  int bInSavepoint;
+  
 #ifdef SQLITE_DEBUG
   struct Fts5TransactionState ts;
 #endif
 };
 
@@ -2613,13 +2613,11 @@
   sqlite3_vtab *pVtab,            /* Virtual table handle */
   const char *zName               /* New name of table */
 ){
   int rc;
   Fts5FullTable *pTab = (Fts5FullTable*)pVtab;
-  pTab->bInSavepoint = 1;
   rc = sqlite3Fts5StorageRename(pTab->pStorage, zName);
-  pTab->bInSavepoint = 0;
   return rc;
 }
 
 int sqlite3Fts5FlushToDisk(Fts5Table *pTab){
   fts5TripCursors((Fts5FullTable*)pTab);
@@ -2632,30 +2630,16 @@
 ** Flush the contents of the pending-terms table to disk.
 */
 static int fts5SavepointMethod(sqlite3_vtab *pVtab, int iSavepoint){
   Fts5FullTable *pTab = (Fts5FullTable*)pVtab;
   int rc = SQLITE_OK;
-  char *zSql = 0;
+
   fts5CheckTransactionState(pTab, FTS5_SAVEPOINT, iSavepoint);
-
-  if( pTab->bInSavepoint==0 ){
-    zSql = sqlite3_mprintf("INSERT INTO %Q.%Q(%Q) VALUES('flush')",
-        pTab->p.pConfig->zDb, pTab->p.pConfig->zName, pTab->p.pConfig->zName
-    );
-    if( zSql ){
-      pTab->bInSavepoint = 1;
-      rc = sqlite3_exec(pTab->p.pConfig->db, zSql, 0, 0, 0);
-      pTab->bInSavepoint = 0;
-      sqlite3_free(zSql);
-    }else{
-      rc = SQLITE_NOMEM;
-    }
-    if( rc==SQLITE_OK ){
-      pTab->iSavepoint = iSavepoint+1;
-    }
-  }
-
+  rc = sqlite3Fts5FlushToDisk((Fts5Table*)pVtab);
+  if( rc==SQLITE_OK ){
+    pTab->iSavepoint = iSavepoint+1;
+  }
   return rc;
 }
 
 /*
 ** The xRelease() method.
@@ -2912,11 +2896,11 @@
 /*
 ** Run an integrity check on the FTS5 data structures.  Return a string
 ** if anything is found amiss.  Return a NULL pointer if everything is
 ** OK.
 */
-static int fts5Integrity(
+static int fts5IntegrityMethod(
   sqlite3_vtab *pVtab,    /* the FTS5 virtual table to check */
   const char *zSchema,    /* Name of schema in which this table lives */
   const char *zTabname,   /* Name of the table itself */
   int isQuick,            /* True if this is a quick-check */
   char **pzErr            /* Write error message here */
@@ -2970,11 +2954,11 @@
     /* xRename       */ fts5RenameMethod,
     /* xSavepoint    */ fts5SavepointMethod,
     /* xRelease      */ fts5ReleaseMethod,
     /* xRollbackTo   */ fts5RollbackToMethod,
     /* xShadowName   */ fts5ShadowName,
-    /* xIntegrity    */ fts5Integrity
+    /* xIntegrity    */ fts5IntegrityMethod
   };
 
   int rc;
   Fts5Global *pGlobal = 0;
 

--- a/ext/fts5/test/fts5misc.test
+++ b/ext/fts5/test/fts5misc.test
@@ -89,11 +89,10 @@
   CREATE VIRTUAL TABLE vt0 USING fts5(c0);
   BEGIN TRANSACTION;
   INSERT INTO vt0(c0) VALUES ('xyz');
 }
 
-breakpoint
 do_execsql_test 2.2.2 {
   ALTER TABLE t0 RENAME TO t1;
 }
 do_execsql_test 2.2.3 {
   INSERT INTO vt0(vt0) VALUES('integrity-check');
@@ -498,8 +497,23 @@
 } {assertionfaultproblem}
 do_execsql_test 17.5 {
   SELECT c0 FROM t0 WHERE c0 GLOB '*faul*';
 } {assertionfaultproblem}
 
+#-------------------------------------------------------------------------
+reset_db
+do_execsql_test 18.0 {
+  BEGIN;
+    CREATE VIRTUAL TABLE t1 USING fts5(text);
+    ALTER TABLE t1 RENAME TO t2;
+}
+
+do_execsql_test 18.1 {
+    DROP TABLE t2;
+}
+
+do_execsql_test 18.2 {
+  COMMIT;
+}
 
 finish_test