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

third_party/sqlite/src/src/pragma.c

 /*
 ** 2003 April 6
 **
 ** 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.
 **
@@ skipping 718 matching lines @@
     sqlite3VdbeAddOp2(v, OP_Integer, iLimit, 1);
     addr = sqlite3VdbeAddOp1(v, OP_IncrVacuum, iDb); VdbeCoverage(v);
     sqlite3VdbeAddOp1(v, OP_ResultRow, 1);
     sqlite3VdbeAddOp2(v, OP_AddImm, 1, -1);
     sqlite3VdbeAddOp2(v, OP_IfPos, 1, addr); VdbeCoverage(v);
     sqlite3VdbeJumpHere(v, addr);
     break;
   }
 #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
   **  PRAGMA [schema.]cache_size=N
   **
   ** The first form reports the current local setting for the
   ** page cache size. The second form sets the local
   ** page cache size value.  If N is positive then that is the
   ** number of pages in the cache.  If N is negative, then the
   ** number of pages is adjusted so that the cache uses -N kibibytes
@@ skipping 1520 matching lines @@
   pName = pragmaLocate(zName+7);
   if( pName==0 ) return 0;
   if( (pName->mPragFlg & (PragFlg_Result0|PragFlg_Result1))==0 ) return 0;
   assert( sqlite3HashFind(&db->aModule, zName)==0 );
   return sqlite3VtabCreateModule(db, zName, &pragmaVtabModule, (void*)pName, 0);
 }
 
 #endif /* SQLITE_OMIT_VIRTUALTABLE */
 
 #endif /* SQLITE_OMIT_PRAGMA */