[sql] SQLite patch to implement "smart" auto-vacuum.

third_party/sqlite/src/src/pragma.c

Index: third_party/sqlite/src/src/pragma.c
diff --git a/third_party/sqlite/src/src/pragma.c b/third_party/sqlite/src/src/pragma.c
index b1775a4082a3a0135f962d8aa37d8809adcd6c4c..1d5ebfca098d3f7b7f7e654b80b3e1cb65b2bffb 100644
--- a/third_party/sqlite/src/src/pragma.c
+++ b/third_party/sqlite/src/src/pragma.c
@@ -736,6 +736,27 @@ void sqlite3Pragma(
   }
 #endif
 
+  /*
+  **  PRAGMA [schema.]auto_vacuum_slack_pages(N)
+  **
+  ** Control chunk size of auto-vacuum.
+  */
+#ifndef SQLITE_OMIT_AUTOVACUUM
+  case PragTyp_AUTO_VACUUM_SLACK_PAGES: {
+    Btree *pBt = pDb->pBt;
+    assert( pBt!=0 );
+    if( !zRight ){
+      returnSingleInt(v, sqlite3BtreeGetAutoVacuumSlackPages(pBt));
+    }else{
+      int nPages = 8;
+      if( sqlite3GetInt32(zRight, &nPages) ){
+        sqlite3BtreeSetAutoVacuumSlackPages(pBt, nPages);
+      }
+    }
+    break;
+  }
+#endif
+
 #ifndef SQLITE_OMIT_PAGER_PRAGMAS
   /*
   **  PRAGMA [schema.]cache_size