sql: Fix bug with multiple dumps.

The statistic ids are unique, so they will create primary key conflicts
on multiple dumps. The solution is to use both the stat id and the dump
id as primary keys.

Change-Id: I9b8e5cf6b0ca5f96f4e09302f9ceb517232b43af

src/base/stats/sql.cc

@@ -95,21 +95,23 @@ bool OutputSQL::create_tables() {
   std::string scalar_value_sql =
       "drop table if exists scalarValue;"
       "create table scalarValue ("
-          "id int primary key,"
+          "id int,"
           "dump int,"
-          "value real);";
+          "value real,"
+          "primary key (id, dump));";
 
   std::string vector_value_sql =
       "drop table if exists vectorValue;"
       "create table vectorValue ("
-          "id int primary key,"
+          "id int,"
           "dump int,"
-          "value blob);";
+          "value blob,"
+          "primary key (id, dump));";
 
   std::string dist_value_sql =
       "drop table if exists distValue;"
       "create table distValue ("
-          "id int primary key,"
+          "id int,"
           "dump int,"
           "sum real,"
           "squares real,"
@@ -121,7 +123,8 @@ bool OutputSQL::create_tables() {
           "min_val real,"
           "max_val real,"
           "underflow real,"
-          "overflow real);";
+          "overflow real,"
+          "primary key (id, dump));";
 
   std::string dump_desc_sql =
       "drop table if exists dumpDesc;"