From 6b24994f08a37739b359aed6950f87286aa562df Mon Sep 17 00:00:00 2001
From: Eliot Horowitz <eliot@10gen.com>
Date: Wed, 11 Jul 2012 15:23:59 -0400
Subject: SERVER-6414 - use regular file io, not mmap for external sort

Conflicts:

	db/extsort.cpp
	db/extsort.h
---
 db/extsort.cpp | 72 ++++++++++++++++++++++++++++++++++++++++++++++++----------
 db/extsort.h   |  8 ++++---
 2 files changed, 65 insertions(+), 15 deletions(-)

diff --git a/db/extsort.cpp b/db/extsort.cpp
index 0cc36f159ed..e0d4d0cf93c 100644
--- a/db/extsort.cpp
+++ b/db/extsort.cpp
@@ -217,24 +217,72 @@ namespace mongo {
     // -----------------------------------
 
     BSONObjExternalSorter::FileIterator::FileIterator( string file ) {
-        unsigned long long length;
-        _buf = (char*)_file.map( file.c_str() , length , MemoryMappedFile::SEQUENTIAL );
-        massert( 10308 ,  "mmap failed" , _buf );
-        assert( length == (unsigned long long) file_size( file ) );
-        _end = _buf + length;
+        _file = ::open( file.c_str(), O_CREAT | O_RDWR | O_NOATIME , S_IRUSR | S_IWUSR );
+        massert( 16392, 
+                 str::stream() << "FileIterator can't open file: " 
+                 << file << errnoWithDescription(), 
+                 _file >= 0 );
+
+#ifdef POSIX_FADV_DONTNEED
+        posix_fadvise(_file, 0, 0, POSIX_FADV_SEQUENTIAL | POSIX_FADV_DONTNEED);
+#endif
+
+        _length = (unsigned long long)boost::filesystem::file_size( file );
+        _readSoFar = 0;
+    }
+
+    BSONObjExternalSorter::FileIterator::~FileIterator() {
+        if ( _file >= 0 )
+            close( _file );
     }
-    BSONObjExternalSorter::FileIterator::~FileIterator() {}
 
     bool BSONObjExternalSorter::FileIterator::more() {
-        return _buf < _end;
+        return _readSoFar < _length;
     }
 
+    
+    bool BSONObjExternalSorter::FileIterator::_read( char* buf, ssize_t count ) {
+        ssize_t total = 0;
+        while ( total < count ) {
+            ssize_t now = ::read( _file, buf, count );
+            if ( now < 0 ) {
+                log() << "read failed for BSONObjExternalSorter " << errnoWithDescription() << endl;
+                return false;
+            }
+            if ( now == 0 ) {
+                return false;
+            }
+            total += now;
+            buf += now;
+        }
+        return true;
+    }
+    
     BSONObjExternalSorter::Data BSONObjExternalSorter::FileIterator::next() {
-        BSONObj o( _buf );
-        _buf += o.objsize();
-        DiskLoc * l = (DiskLoc*)_buf;
-        _buf += 8;
-        return Data( o , *l );
+        // read BSONObj
+
+        int size;
+        assert( _read( reinterpret_cast<char*>(&size), 4 ) );
+        char* buf = reinterpret_cast<char*>( malloc( sizeof(unsigned) + size ) );
+        assert( buf );
+
+        memset( buf, 0, 4 ); // for Holder
+        memcpy( buf+sizeof(unsigned), reinterpret_cast<char*>(&size), sizeof(int) ); // size of doc
+        if ( ! _read( buf + sizeof(unsigned) + sizeof(int), size-sizeof(int) ) ) { // doc content
+            free( buf );
+            msgasserted( 16394, "reading doc for external sort failed" );
+        }
+        
+        // read DiskLoc
+        DiskLoc l;
+        if ( ! _read( reinterpret_cast<char*>(&l), 8 ) ) {
+            free( buf );
+            msgasserted( 16393, "reading DiskLoc for external sort failed" );            
+        }
+        _readSoFar += 8 + size;
+        
+        BSONObj::Holder* h = reinterpret_cast<BSONObj::Holder*>(buf);
+        return Data( BSONObj(h), l );
     }
 
 }
diff --git a/db/extsort.h b/db/extsort.h
index ae6a334f77a..04f9e5e6f85 100644
--- a/db/extsort.h
+++ b/db/extsort.h
@@ -76,9 +76,11 @@ namespace mongo {
             bool more();
             Data next();
         private:
-            MemoryMappedFile _file;
-            char * _buf;
-            char * _end;
+            bool _read( char* buf, ssize_t count );
+
+            int _file;
+            unsigned long long _length;
+            unsigned long long _readSoFar;
         };
 
     public:
-- 
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