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Fix for backward cursors with ORDER BY.

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This commit is contained in:
Vadim B. Mikheev 1997-10-15 06:36:36 +00:00
parent 9acf938c10
commit 78351f422b
2 changed files with 113 additions and 25 deletions
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135
src/backend/utils/sort/psort.c
View File

@ -7,7 +7,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/utils/sort/Attic/psort.c,v 1.25 1997/09/26 20:05:47 momjian Exp $
* $Header: /cvsroot/pgsql/src/backend/utils/sort/Attic/psort.c,v 1.26 1997/10/15 06:36:08 vadim Exp $
*
* NOTES
* Sorts the first relation into the second relation.
@ -80,7 +80,12 @@ static int _psort_cmp (HeapTuple *ltup, HeapTuple *rtup);
#define TEMPDIR "./"
static long shortzero = 0; /* used to delimit runs */
/*
* tlenzero used to delimit runs; both vars below must have
* the same size as HeapTuple->t_len
*/
static unsigned int tlenzero = 0;
static unsigned int tlendummy;
static TupleDesc PsortTupDesc;
static ScanKey PsortKeys; /* used by _psort_cmp */
@ -150,6 +155,7 @@ psort_begin(Sort * node, int nkeys, ScanKey key)
PS(node)->tupcount = 0;
PS(node)->using_tape_files = false;
PS(node)->all_fetched = false;
PS(node)->psort_grab_file = NULL;
PS(node)->memtuples = NULL;
@ -219,21 +225,24 @@ inittapes(Sort * node)
* GETTUP - reads the tuple
*
* Note:
* LEN field must be a short; FP is a stream
* LEN field must be as HeapTuple->t_len; FP is a stream
*/
#define PUTTUP(NODE, TUP, FP) do {\
((Psortstate *)NODE->psortstate)->BytesWritten += (TUP)->t_len; \
fwrite((char *)TUP, (TUP)->t_len, 1, FP);} while (0)
#define ENDRUN(FP) fwrite((char *)&shortzero, sizeof (shortzero), 1, FP)
#define GETLEN(LEN, FP) fread((char *)&(LEN), sizeof (shortzero), 1, FP)
fwrite((char *)TUP, (TUP)->t_len, 1, FP); \
fwrite((char *)&((TUP)->t_len), sizeof (tlendummy), 1, FP); \
} while (0)
#define ENDRUN(FP) fwrite((char *)&tlenzero, sizeof (tlenzero), 1, FP)
#define GETLEN(LEN, FP) fread((char *)&(LEN), sizeof (tlenzero), 1, FP)
#define ALLOCTUP(LEN) ((HeapTuple)palloc((unsigned)LEN))
#define GETTUP(NODE, TUP, LEN, FP) do {\
IncrProcessed(); \
((Psortstate *)NODE->psortstate)->BytesRead += (LEN) - sizeof (shortzero); \
fread((char *)(TUP) + sizeof (shortzero), (LEN) - sizeof (shortzero), 1, FP);} \
while (0)
((Psortstate *)NODE->psortstate)->BytesRead += (LEN) - sizeof (tlenzero); \
fread((char *)(TUP) + sizeof (tlenzero), (LEN) - sizeof (tlenzero), 1, FP); \
fread((char *)&tlendummy, sizeof (tlendummy), 1, FP); \
} while (0)
#define SETTUPLEN(TUP, LEN) (TUP)->t_len = LEN
/*
@ -629,11 +638,11 @@ merge(Sort * node, struct tape * dest)
register struct tape *lasttp; /* (TAPE[P]) */
register struct tape *tp;
struct leftist *tuples;
FILE *destfile;
int times; /* runs left to merge */
int outdummy; /* complete dummy runs */
short fromtape;
long tuplen;
FILE *destfile;
int times; /* runs left to merge */
int outdummy; /* complete dummy runs */
short fromtape;
unsigned int tuplen;
Assert(node != (Sort *) NULL);
Assert(PS(node) != (Psortstate *) NULL);
@ -767,16 +776,20 @@ dumptuples(FILE * file, Sort * node)
HeapTuple
psort_grabtuple(Sort * node, bool * should_free)
{
register HeapTuple tup;
long tuplen;
register HeapTuple tup;
Assert(node != (Sort *) NULL);
Assert(PS(node) != (Psortstate *) NULL);
if (PS(node)->using_tape_files == true)
{
if (!feof(PS(node)->psort_grab_file))
unsigned int tuplen;
*should_free = true;
if (ScanDirectionIsForward (node->plan.state->es_direction))
{
if (PS(node)->all_fetched)
return NULL;
if (GETLEN(tuplen, PS(node)->psort_grab_file) && tuplen != 0)
{
tup = (HeapTuple) palloc((unsigned) tuplen);
@ -784,25 +797,99 @@ psort_grabtuple(Sort * node, bool * should_free)
GETTUP(node, tup, tuplen, PS(node)->psort_grab_file);
/* Update current merged sort file position */
PS(node)->psort_current += tuplen;
*should_free = true;
PS(node)->psort_current += tuplen + sizeof (tlendummy);
return tup;
}
else
{
PS(node)->all_fetched = true;
return NULL;
}
}
/* Backward */
if (PS(node)->psort_current <= sizeof (tlendummy))
return NULL;
/*
* if all tuples are fetched already then we return last tuple,
* else - tuple before last returned.
*/
if (PS(node)->all_fetched)
{
/* psort_current is pointing to the zero tuplen at the end of file */
fseek(PS(node)->psort_grab_file,
PS(node)->psort_current - sizeof (tlendummy), SEEK_SET);
GETLEN(tuplen, PS(node)->psort_grab_file);
if (PS(node)->psort_current < tuplen)
elog (FATAL, "psort_grabtuple: too big last tuple len in backward scan");
PS(node)->all_fetched = false;
}
else
return NULL;
{
/* move to position of end tlen of prev tuple */
PS(node)->psort_current -= sizeof (tlendummy);
fseek(PS(node)->psort_grab_file, PS(node)->psort_current, SEEK_SET);
GETLEN(tuplen, PS(node)->psort_grab_file); /* get tlen of prev tuple */
if (tuplen == 0)
elog (FATAL, "psort_grabtuple: tuplen is 0 in backward scan");
if (PS(node)->psort_current <= tuplen + sizeof (tlendummy))
{ /* prev tuple should be first one */
if (PS(node)->psort_current != tuplen)
elog (FATAL, "psort_grabtuple: first tuple expected in backward scan");
PS(node)->psort_current = 0;
fseek(PS(node)->psort_grab_file, PS(node)->psort_current, SEEK_SET);
return NULL;
}
/*
* Get position of prev tuple. This tuple becomes current tuple
* now and we have to return previous one.
*/
PS(node)->psort_current -= tuplen;
/* move to position of end tlen of prev tuple */
fseek(PS(node)->psort_grab_file,
PS(node)->psort_current - sizeof (tlendummy), SEEK_SET);
GETLEN(tuplen, PS(node)->psort_grab_file);
if (PS(node)->psort_current < tuplen + sizeof (tlendummy))
elog (FATAL, "psort_grabtuple: too big tuple len in backward scan");
}
/*
* move to prev (or last) tuple start position + sizeof(t_len)
*/
fseek(PS(node)->psort_grab_file,
PS(node)->psort_current - tuplen, SEEK_SET);
tup = (HeapTuple) palloc((unsigned) tuplen);
SETTUPLEN(tup, tuplen);
GETTUP(node, tup, tuplen, PS(node)->psort_grab_file);
return tup; /* file position is equal to psort_current */
}
else
{
if (PS(node)->psort_current < PS(node)->tupcount)
*should_free = false;
if (ScanDirectionIsForward (node->plan.state->es_direction))
{
*should_free = false;
return (PS(node)->memtuples[PS(node)->psort_current++]);
if (PS(node)->psort_current < PS(node)->tupcount)
return (PS(node)->memtuples[PS(node)->psort_current++]);
else
{
PS(node)->all_fetched = true;
return NULL;
}
}
else
/* Backward */
if (PS(node)->psort_current <= 0)
return NULL;
/*
* if all tuples are fetched already then we return last tuple,
* else - tuple before last returned.
*/
if (PS(node)->all_fetched)
PS(node)->all_fetched = false;
else
{
PS(node)->psort_current--; /* last returned tuple */
if (PS(node)->psort_current <= 0)
return NULL;
}
return (PS(node)->memtuples[PS(node)->psort_current - 1]);
}
}

3
src/include/utils/psort.h
View File

@ -6,7 +6,7 @@
*
* Copyright (c) 1994, Regents of the University of California
*
* $Id: psort.h,v 1.13 1997/09/18 14:42:35 vadim Exp $
* $Id: psort.h,v 1.14 1997/10/15 06:36:36 vadim Exp $
*
*-------------------------------------------------------------------------
*/
@ -62,6 +62,7 @@ typedef struct Psortstate
long psort_current; /* could be file offset, or array index */
long psort_saved; /* could be file offset, or array index */
bool using_tape_files;
bool all_fetched; /* this is for cursors */
HeapTuple *memtuples;
} Psortstate;