add FTS3 _backward_compatibility mode to let apps use FTS1 or 2.

bug:2651952
this mode was previously available in Eclair and below. this mode was removed
by me for no particular reason in Froyo.
this change doesn't bring in any new modules into sqlite. just
allows FTS1 or 2 apps be used with FTS3 running in backward compatibility mode

Change-Id: Id5d72b440a378dd6d6703ce99b5d3d70ffd0c80f

dist/Android.mk

@@ -21,7 +21,7 @@ endif
 #   SQLITE_TEMP_STORE=3 causes all TEMP files to go into RAM. and thats the behavior we want
 #   SQLITE_ENABLE_FTS3   enables usage of FTS3 - NOT FTS1 or 2.
 #   SQLITE_DEFAULT_AUTOVACUUM=1  causes the databases to be subject to auto-vacuum
-LOCAL_CFLAGS += -DHAVE_USLEEP=1 -DSQLITE_DEFAULT_JOURNAL_SIZE_LIMIT=1048576 -DSQLITE_THREADSAFE=1 -DNDEBUG=1 -DSQLITE_ENABLE_MEMORY_MANAGEMENT=1 -DSQLITE_DEFAULT_AUTOVACUUM=1 -DSQLITE_TEMP_STORE=3 -DSQLITE_ENABLE_FTS3
+LOCAL_CFLAGS += -DHAVE_USLEEP=1 -DSQLITE_DEFAULT_JOURNAL_SIZE_LIMIT=1048576 -DSQLITE_THREADSAFE=1 -DNDEBUG=1 -DSQLITE_ENABLE_MEMORY_MANAGEMENT=1 -DSQLITE_DEFAULT_AUTOVACUUM=1 -DSQLITE_TEMP_STORE=3 -DSQLITE_ENABLE_FTS3 -DSQLITE_ENABLE_FTS3_BACKWARDS
 
 ifneq ($(TARGET_SIMULATOR),true)
 LOCAL_SHARED_LIBRARIES := libdl

dist/sqlite3.c

@@ -95405,7 +95405,9 @@ SQLITE_API int sqlite3_complete16(const void *zSql){
 extern "C" {
 #endif  /* __cplusplus */
-SQLITE_PRIVATE int sqlite3Fts3Init(sqlite3 *db);
+// Begin Android Change
+SQLITE_PRIVATE int sqlite3Fts3Init(sqlite3 *db, const char* registerAs);
+// End Android Change
 #if 0
 }  /* extern "C" */
@@ -97148,6 +97150,9 @@ static int openDatabase(
   }
 #ifdef SQLITE_ENABLE_FTS1
+// Begin Android change
+#error "Do not enable FTS1 on Android as FTS3_BACKWARDS has been in use"
+// End Android add
   if( !db->mallocFailed ){
     extern int sqlite3Fts1Init(sqlite3*);
     rc = sqlite3Fts1Init(db);
@@ -97155,6 +97160,9 @@ static int openDatabase(
 #endif
 #ifdef SQLITE_ENABLE_FTS2
+// Begin Android change
+#error "Do not enable FTS2 on Android as FTS3_BACKWARDS has been in use"
+// End Android add
   if( !db->mallocFailed && rc==SQLITE_OK ){
     extern int sqlite3Fts2Init(sqlite3*);
     rc = sqlite3Fts2Init(db);
@@ -97162,9 +97170,24 @@ static int openDatabase(
 #endif
 #ifdef SQLITE_ENABLE_FTS3
-  if( !db->mallocFailed && rc==SQLITE_OK ){
-    rc = sqlite3Fts3Init(db);
-  }
+  // Begin Android change
+  #ifdef SQLITE_ENABLE_FTS3_BACKWARDS
+    /* Also register as fts1 and fts2, for backwards compatability on
+    ** systems known to have never seen a pre-fts3 database.
+    */
+    if( !db->mallocFailed && rc==SQLITE_OK ){
+      rc = sqlite3Fts3Init(db, "fts1");
+    }
+
+    if( !db->mallocFailed && rc==SQLITE_OK ){
+      rc = sqlite3Fts3Init(db, "fts2");
+    }
+  #endif
+
+    if( !db->mallocFailed && rc==SQLITE_OK ){
+      rc = sqlite3Fts3Init(db, "fts3");
+    }
+  // End Android change
 #endif
 #ifdef SQLITE_ENABLE_ICU
@@ -101095,7 +101118,10 @@ SQLITE_PRIVATE void sqlite3Fts3IcuTokenizerModule(sqlite3_tokenizer_module const
 ** SQLite. If fts3 is built as a dynamically loadable extension, this
 ** function is called by the sqlite3_extension_init() entry point.
 */
-SQLITE_PRIVATE int sqlite3Fts3Init(sqlite3 *db){
+// Begin Android change
+SQLITE_PRIVATE int sqlite3Fts3Init(sqlite3 *db, const char* registerAs){
+// End Android change
+
   int rc = SQLITE_OK;
   Fts3Hash *pHash = 0;
   const sqlite3_tokenizer_module *pSimple = 0;
@@ -101147,8 +101173,11 @@ SQLITE_PRIVATE int sqlite3Fts3Init(sqlite3 *db){
    && SQLITE_OK==(rc = sqlite3_overload_function(db, "matchinfo", -1))
    && SQLITE_OK==(rc = sqlite3_overload_function(db, "optimize", 1))
   ){
+    // Begin Android change
+    /* Also register as fts1 and fts2 */
     return sqlite3_create_module_v2(
-        db, "fts3", &fts3Module, (void *)pHash, hashDestroy
+        db, registerAs, &fts3Module, (void *)pHash, hashDestroy
+    // End Android change
     );
   }