public RC SorterRewind(Context ctx, VdbeCursor cursor, ref bool eof)
{
VdbeSorter sorter = cursor.Sorter;
Debug.Assert(sorter != null);
// If no data has been written to disk, then do not do so now. Instead, sort the VdbeSorter.pRecord list. The vdbe layer will read data directly
// from the in-memory list.
if (sorter.PMAs == 0)
{
eof = (sorter.Record == null);
Debug.Assert(sorter.Trees.data = null);
return(VdbeSorterSort(cursor));
}
// Write the current in-memory list to a PMA.
RC rc = VdbeSorterListToPMA(ctx, cursor);
if (rc != RC.OK)
{
return(rc);
}
// Allocate space for aIter[] and aTree[].
int iters = sorter.PMAs; // Number of iterators used
if (iters > SORTER_MAX_MERGE_COUNT)
{
iters = SORTER_MAX_MERGE_COUNT;
}
Debug.Assert(iters > 0);
int n = 2; while (n < iters)
{
n += n; // Power of 2 >= iters
}
int bytes = n * (sizeof(int) + sizeof(VdbeSorterIter)); // Bytes of space required for aIter/aTree
sorter.Iters = (VdbeSorterIter)C._tagalloc(ctx, bytes);
if (sorter.Iters == null)
{
return(RC.NOMEM);
}
sorter.Trees = sorter.Iters[n];
sorter.Trees.length = n;
int newIdx; // Index of new, merged, PMA
VFile temp2 = null; // Second temp file to use
long write2 = 0; // Write offset for pTemp2
do
{
for (newIdx = 0; rc == RC.OK && newIdx * SORTER_MAX_MERGE_COUNT < sorter.PMAs; newIdx++)
{
FileWriter writer; writer._memset(); // Object used to write to disk
// If there are SORTER_MAX_MERGE_COUNT or less PMAs in file pTemp1, initialize an iterator for each of them and break out of the loop.
// These iterators will be incrementally merged as the VDBE layer calls sqlite3VdbeSorterNext().
//
// Otherwise, if pTemp1 contains more than SORTER_MAX_MERGE_COUNT PMAs, initialize interators for SORTER_MAX_MERGE_COUNT of them. These PMAs
// are merged into a single PMA that is written to file pTemp2.
long writes; // Number of bytes in new PMA
rc = VdbeSorterInitMerge(ctx, cursor, ref writes);
Debug.Assert(rc != RC.OK || sorter.Iters[sorter.Trees[1]].File);
if (rc != RC.OK || sorter.PMAs <= SORTER_MAX_MERGE_COUNT)
{
break;
}
// Open the second temp file, if it is not already open.
if (temp2 == null)
{
Debug.Assert(write2 == 0);
rc = VdbeSorterOpenTempFile(ctx, ref temp2);
}
if (rc == RC.OK)
{
bool eof = false;
FileWriterInit(ctx, temp2, ref writer, write2);
FileWriterWriteVarint(writer, writes);
while (rc == RC.OK && !eof)
{
VdbeSorterIter iter = sorter.Iters[sorter.Trees[1]];
Debug.Assert(iter.File);
FileWriterWriteVarint(writer, iter.Key.length);
FileWriterWrite(writer, iter.Key, iter.Key.length);
rc = SorterNext(ctx, cursor, eof);
}
RC rc2 = FileWriterFinish(ctx, writer, write2);
if (rc == RC.OK)
{
rc = rc2;
}
}
}
if (sorter.PMAs <= SORTER_MAX_MERGE_COUNT)
{
break;
}
else
{
VFile tmp = sorter.Temp1;
sorter.PMAs = newIdx;
sorter.Temp1 = temp2;
temp2 = tmp;
sorter.WriteOffset = write2;
sorter.ReadOffset = 0;
write2 = 0;
}
} while (rc == RC.OK);
if (temp2)
{
temp2.CloseAndFree();
}
eof = (sorter.Iters[sorter.Trees[1]].File == null);
return(rc);
}
