Fix a race condition to do with very large index keys in shared-cache mode.

FossilOrigin-Name: fc157dd7f18c94b7ae5f155e1b4a5d7714b7da8c

test/threadtest3.c

@@ -1398,6 +1398,7 @@ static void dynamic_triggers(int nMs){
 
 #include "tt3_checkpoint.c"
 #include "tt3_index.c"
+#include "tt3_lookaside1.c"
 
 int main(int argc, char **argv){
   struct ThreadTest {
@@ -1419,6 +1420,7 @@ int main(int argc, char **argv){
     { checkpoint_starvation_2, "checkpoint_starvation_2", 10000 },
 
     { create_drop_index_1, "create_drop_index_1", 10000 },
+    { lookaside1, "lookaside1", 10000 },
   };
 
   int i;

test/tt3_index.c

@@ -67,8 +67,8 @@ static void create_drop_index_1(int nMs){
   launch_thread(&err, &threads, create_drop_index_thread, 0);
   launch_thread(&err, &threads, create_drop_index_thread, 0);
   launch_thread(&err, &threads, create_drop_index_thread, 0);
-  sqlite3_enable_shared_cache(0);
 
   join_all_threads(&err, &threads);
+  sqlite3_enable_shared_cache(0);
   print_and_free_err(&err);
 }

test/tt3_lookaside1.c

@@ -0,0 +1,99 @@
+/*
+** 2014 December 9
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+**
+**     lookaside1
+*/
+
+/*
+** The test in this file attempts to expose a specific race condition
+** that is suspected to exist at time of writing.
+*/
+
+static char *lookaside1_thread_reader(int iTid, int iArg){
+  Error err = {0};                /* Error code and message */
+  Sqlite db = {0};                /* SQLite database connection */
+
+  opendb(&err, &db, "test.db", 0);
+
+  while( !timetostop(&err) ){
+    sqlite3_stmt *pStmt = 0;
+    int rc;
+
+    sqlite3_prepare_v2(db.db, "SELECT 1 FROM t1", -1, &pStmt, 0);
+    while( sqlite3_step(pStmt)==SQLITE_ROW ){
+      execsql(&err, &db, "SELECT length(x||y||z) FROM t2");
+    }
+    rc = sqlite3_finalize(pStmt);
+    if( err.rc==SQLITE_OK && rc!=SQLITE_OK ){
+      sqlite_error(&err, &db, "finalize");
+    }
+  }
+
+  closedb(&err, &db);
+  print_and_free_err(&err);
+  return sqlite3_mprintf("ok");
+}
+
+static char *lookaside1_thread_writer(int iTid, int iArg){
+  Error err = {0};                /* Error code and message */
+  Sqlite db = {0};                /* SQLite database connection */
+
+  opendb(&err, &db, "test.db", 0);
+
+  do{
+    sql_script(&err, &db, 
+      "BEGIN;"
+        "UPDATE t3 SET i=i+1 WHERE x=1;"
+      "ROLLBACK;"
+    );
+  }while( !timetostop(&err) );
+
+  closedb(&err, &db);
+  print_and_free_err(&err);
+  return sqlite3_mprintf("ok");
+}
+
+
+static void lookaside1(int nMs){
+  Error err = {0};
+  Sqlite db = {0};
+  Threadset threads = {0};
+
+  opendb(&err, &db, "test.db", 1);
+  sql_script(&err, &db, 
+     "CREATE TABLE t1(x PRIMARY KEY) WITHOUT ROWID;"
+     "WITH data(x,y) AS ("
+     "  SELECT 1, quote(randomblob(750)) UNION ALL "
+     "  SELECT x*2, y||y FROM data WHERE x<5) "
+     "INSERT INTO t1 SELECT y FROM data;"
+
+     "CREATE TABLE t3(x PRIMARY KEY,i) WITHOUT ROWID;"
+     "INSERT INTO t3 VALUES(1, 1);"
+
+     "CREATE TABLE t2(x,y,z);"
+     "INSERT INTO t2 VALUES(randomblob(50), randomblob(50), randomblob(50));"
+  );
+  closedb(&err, &db);
+
+  setstoptime(&err, nMs);
+
+  sqlite3_enable_shared_cache(1);
+  launch_thread(&err, &threads, lookaside1_thread_reader, 0);
+  launch_thread(&err, &threads, lookaside1_thread_reader, 0);
+  launch_thread(&err, &threads, lookaside1_thread_reader, 0);
+  launch_thread(&err, &threads, lookaside1_thread_reader, 0);
+  launch_thread(&err, &threads, lookaside1_thread_reader, 0);
+  launch_thread(&err, &threads, lookaside1_thread_writer, 0);
+  join_all_threads(&err, &threads);
+  sqlite3_enable_shared_cache(0);
+  print_and_free_err(&err);
+}