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help / color / mirror / Atom feedFrom: Melanie Plageman <[email protected]>
Subject: [PATCH v7 10/13] Hard-code TBMIterateResult offsets array size
Date: Thu, 15 Feb 2024 20:13:43 -0500
TIDBitmap's TBMIterateResult had a flexible sized array of tuple offsets
but the API always allocated MaxHeapTuplesPerPage OffsetNumbers.
Creating a fixed-size aray of size MaxHeapTuplesPerPage is more clear
for the API user.
---
src/backend/nodes/tidbitmap.c | 29 +++++++----------------------
src/include/nodes/tidbitmap.h | 12 ++++++++++--
2 files changed, 17 insertions(+), 24 deletions(-)
diff --git a/src/backend/nodes/tidbitmap.c b/src/backend/nodes/tidbitmap.c
index e8ab5d78fcc..d2bf8f44d50 100644
--- a/src/backend/nodes/tidbitmap.c
+++ b/src/backend/nodes/tidbitmap.c
@@ -40,7 +40,6 @@
#include <limits.h>
-#include "access/htup_details.h"
#include "common/hashfn.h"
#include "common/int.h"
#include "nodes/bitmapset.h"
@@ -48,14 +47,6 @@
#include "storage/lwlock.h"
#include "utils/dsa.h"
-/*
- * The maximum number of tuples per page is not large (typically 256 with
- * 8K pages, or 1024 with 32K pages). So there's not much point in making
- * the per-page bitmaps variable size. We just legislate that the size
- * is this:
- */
-#define MAX_TUPLES_PER_PAGE MaxHeapTuplesPerPage
-
/*
* When we have to switch over to lossy storage, we use a data structure
* with one bit per page, where all pages having the same number DIV
@@ -67,7 +58,7 @@
* table, using identical data structures. (This is because the memory
* management for hashtables doesn't easily/efficiently allow space to be
* transferred easily from one hashtable to another.) Therefore it's best
- * if PAGES_PER_CHUNK is the same as MAX_TUPLES_PER_PAGE, or at least not
+ * if PAGES_PER_CHUNK is the same as MaxHeapTuplesPerPage, or at least not
* too different. But we also want PAGES_PER_CHUNK to be a power of 2 to
* avoid expensive integer remainder operations. So, define it like this:
*/
@@ -79,7 +70,7 @@
#define BITNUM(x) ((x) % BITS_PER_BITMAPWORD)
/* number of active words for an exact page: */
-#define WORDS_PER_PAGE ((MAX_TUPLES_PER_PAGE - 1) / BITS_PER_BITMAPWORD + 1)
+#define WORDS_PER_PAGE ((MaxHeapTuplesPerPage - 1) / BITS_PER_BITMAPWORD + 1)
/* number of active words for a lossy chunk: */
#define WORDS_PER_CHUNK ((PAGES_PER_CHUNK - 1) / BITS_PER_BITMAPWORD + 1)
@@ -181,7 +172,7 @@ struct TBMIterator
int spageptr; /* next spages index */
int schunkptr; /* next schunks index */
int schunkbit; /* next bit to check in current schunk */
- TBMIterateResult output; /* MUST BE LAST (because variable-size) */
+ TBMIterateResult output;
};
/*
@@ -222,7 +213,7 @@ struct TBMSharedIterator
PTEntryArray *ptbase; /* pagetable element array */
PTIterationArray *ptpages; /* sorted exact page index list */
PTIterationArray *ptchunks; /* sorted lossy page index list */
- TBMIterateResult output; /* MUST BE LAST (because variable-size) */
+ TBMIterateResult output;
};
/* Local function prototypes */
@@ -390,7 +381,7 @@ tbm_add_tuples(TIDBitmap *tbm, const ItemPointer tids, int ntids,
bitnum;
/* safety check to ensure we don't overrun bit array bounds */
- if (off < 1 || off > MAX_TUPLES_PER_PAGE)
+ if (off < 1 || off > MaxHeapTuplesPerPage)
elog(ERROR, "tuple offset out of range: %u", off);
/*
@@ -692,12 +683,7 @@ tbm_begin_iterate(TIDBitmap *tbm)
Assert(tbm->iterating != TBM_ITERATING_SHARED);
- /*
- * Create the TBMIterator struct, with enough trailing space to serve the
- * needs of the TBMIterateResult sub-struct.
- */
- iterator = (TBMIterator *) palloc(sizeof(TBMIterator) +
- MAX_TUPLES_PER_PAGE * sizeof(OffsetNumber));
+ iterator = palloc(sizeof(TBMIterator));
iterator->tbm = tbm;
/*
@@ -1467,8 +1453,7 @@ tbm_attach_shared_iterate(dsa_area *dsa, dsa_pointer dp)
* Create the TBMSharedIterator struct, with enough trailing space to
* serve the needs of the TBMIterateResult sub-struct.
*/
- iterator = (TBMSharedIterator *) palloc0(sizeof(TBMSharedIterator) +
- MAX_TUPLES_PER_PAGE * sizeof(OffsetNumber));
+ iterator = (TBMSharedIterator *) palloc0(sizeof(TBMSharedIterator));
istate = (TBMSharedIteratorState *) dsa_get_address(dsa, dp);
diff --git a/src/include/nodes/tidbitmap.h b/src/include/nodes/tidbitmap.h
index 1945f0639bf..432fae52962 100644
--- a/src/include/nodes/tidbitmap.h
+++ b/src/include/nodes/tidbitmap.h
@@ -22,6 +22,7 @@
#ifndef TIDBITMAP_H
#define TIDBITMAP_H
+#include "access/htup_details.h"
#include "storage/itemptr.h"
#include "utils/dsa.h"
@@ -41,9 +42,16 @@ typedef struct TBMIterateResult
{
BlockNumber blockno; /* page number containing tuples */
int ntuples; /* -1 indicates lossy result */
- bool recheck; /* should the tuples be rechecked? */
/* Note: recheck is always true if ntuples < 0 */
- OffsetNumber offsets[FLEXIBLE_ARRAY_MEMBER];
+ bool recheck; /* should the tuples be rechecked? */
+
+ /*
+ * The maximum number of tuples per page is not large (typically 256 with
+ * 8K pages, or 1024 with 32K pages). So there's not much point in making
+ * the per-page bitmaps variable size. We just legislate that the size is
+ * this:
+ */
+ OffsetNumber offsets[MaxHeapTuplesPerPage];
} TBMIterateResult;
/* function prototypes in nodes/tidbitmap.c */
--
2.40.1
--kqqpqghcwbcc3dt5
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
filename="v7-0011-Separate-TBM-Shared-Iterator-and-TBMIterateResult.patch"
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