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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2000-10-24 03:34:53 +0000 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2000-10-24 03:34:53 +0000 |
| commit | a9b6b01ee8a70d6abe8e5a56f18115c804fd10f4 (patch) | |
| tree | 3e90a8b6586d57e5233bb6de36d39db1f441e263 /src | |
| parent | 711c9f30f80fa8756fb7b04b3d49a85e8ecad539 (diff) | |
| download | postgresql-a9b6b01ee8a70d6abe8e5a56f18115c804fd10f4.tar.gz postgresql-a9b6b01ee8a70d6abe8e5a56f18115c804fd10f4.zip | |
Reconsider page size for large objects: rather than stuffing disk pages
as full as possible, seems better to use a tuple size around BLCKSZ/4
so that less space is wasted when a LO tuple is updated. Also, this
lets us use a logical page size that's an exact power of two, avoiding
partial-page writes when client is sending us stuff in power-of-2
buffer chunks.
Diffstat (limited to 'src')
| -rw-r--r-- | src/include/catalog/catversion.h | 4 | ||||
| -rw-r--r-- | src/include/storage/large_object.h | 19 |
2 files changed, 14 insertions, 9 deletions
diff --git a/src/include/catalog/catversion.h b/src/include/catalog/catversion.h index f6fd284f34d..56f515b662a 100644 --- a/src/include/catalog/catversion.h +++ b/src/include/catalog/catversion.h @@ -37,7 +37,7 @@ * Portions Copyright (c) 1996-2000, PostgreSQL, Inc * Portions Copyright (c) 1994, Regents of the University of California * - * $Id: catversion.h,v 1.52 2000/10/24 01:38:41 tgl Exp $ + * $Id: catversion.h,v 1.53 2000/10/24 03:34:15 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -53,6 +53,6 @@ */ /* yyyymmddN */ -#define CATALOG_VERSION_NO 200010232 +#define CATALOG_VERSION_NO 200010233 #endif diff --git a/src/include/storage/large_object.h b/src/include/storage/large_object.h index 6bb0c4fcf2e..c7630124811 100644 --- a/src/include/storage/large_object.h +++ b/src/include/storage/large_object.h @@ -8,7 +8,7 @@ * Portions Copyright (c) 1996-2000, PostgreSQL, Inc * Portions Copyright (c) 1994, Regents of the University of California * - * $Id: large_object.h,v 1.18 2000/10/24 01:38:43 tgl Exp $ + * $Id: large_object.h,v 1.19 2000/10/24 03:34:53 tgl Exp $ * *------------------------------------------------------------------------- */ @@ -47,13 +47,18 @@ typedef struct LargeObjectDesc { /* * Each "page" (tuple) of a large object can hold this much data * - * Calculation is max tuple size less tuple header, loid field (Oid), - * pageno field (int32), and varlena header of data (int32). Note we - * assume none of the fields will be NULL, hence no need for null bitmap. + * We could set this as high as BLCKSZ less some overhead, but it seems + * better to make it a smaller value, so that not as much space is used + * up when a page-tuple is updated. Note that the value is deliberately + * chosen large enough to trigger the tuple toaster, so that we will + * attempt to compress page tuples in-line. (But they won't be moved off + * unless the user creates a toast-table for pg_largeobject...) + * + * Also, it seems to be a smart move to make the page size be a power of 2, + * since clients will often be written to send data in power-of-2 blocks. + * This avoids unnecessary tuple updates caused by partial-page writes. */ -#define LOBLKSIZE (MaxTupleSize \ - - MAXALIGN(offsetof(HeapTupleHeaderData, t_bits)) \ - - sizeof(Oid) - sizeof(int32) * 2) +#define LOBLKSIZE (BLCKSZ / 4) /* |