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Avoid unnecessary zeroing of fields in the MemPage object that are going

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to be reinitialized before use anyhow.  A smaller and faster binary results.

FossilOrigin-Name: 01ada3d1068476f90dcae02cb089001ea4bcc23d
This commit is contained in:
drh
2016-12-09 16:02:00 +00:00
parent e0568d6fb8
commit a2ee589c46
6 changed files with 42 additions and 36 deletions
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32
src/btreeInt.h
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@@ -259,37 +259,39 @@ typedef struct CellInfo CellInfo;
#define PTF_LEAF 0x08
/*
** As each page of the file is loaded into memory, an instance of the following
** structure is appended and initialized to zero. This structure stores
** information about the page that is decoded from the raw file page.
** An instance of this object stores information about each a single database
** page that has been loaded into memory. The information in this object
** is derived from the raw on-disk page content.
**
** The pParent field points back to the parent page. This allows us to
** walk up the BTree from any leaf to the root. Care must be taken to
** unref() the parent page pointer when this page is no longer referenced.
** The pageDestructor() routine handles that chore.
** As each database page is loaded into memory, the pager allocats an
** instance of this object and zeros the first 8 bytes. (This is the
** "extra" information associated with each page of the pager.)
**
** Access to all fields of this structure is controlled by the mutex
** stored in MemPage.pBt->mutex.
*/
struct MemPage {
u8 isInit; /* True if previously initialized. MUST BE FIRST! */
u8 nOverflow; /* Number of overflow cell bodies in aCell[] */
u8 bBusy; /* Prevent endless loops on corrupt database files */
u8 intKey; /* True if table b-trees. False for index b-trees */
u8 intKeyLeaf; /* True if the leaf of an intKey table */
Pgno pgno; /* Page number for this page */
/* Only the first 8 bytes (above) are zeroed by pager.c when a new page
** is allocated. All fields that follow must be initialized before use */
u8 leaf; /* True if a leaf page */
u8 hdrOffset; /* 100 for page 1. 0 otherwise */
u8 childPtrSize; /* 0 if leaf==1. 4 if leaf==0 */
u8 max1bytePayload; /* min(maxLocal,127) */
u8 bBusy; /* Prevent endless loops on corrupt database files */
u8 nOverflow; /* Number of overflow cell bodies in aCell[] */
u16 maxLocal; /* Copy of BtShared.maxLocal or BtShared.maxLeaf */
u16 minLocal; /* Copy of BtShared.minLocal or BtShared.minLeaf */
u16 cellOffset; /* Index in aData of first cell pointer */
u16 nFree; /* Number of free bytes on the page */
u16 nCell; /* Number of cells on this page, local and ovfl */
u16 maskPage; /* Mask for page offset */
u16 aiOvfl[5]; /* Insert the i-th overflow cell before the aiOvfl-th
u16 aiOvfl[4]; /* Insert the i-th overflow cell before the aiOvfl-th
** non-overflow cell */
u8 *apOvfl[5]; /* Pointers to the body of overflow cells */
u8 *apOvfl[4]; /* Pointers to the body of overflow cells */
BtShared *pBt; /* Pointer to BtShared that this page is part of */
u8 *aData; /* Pointer to disk image of the page data */
u8 *aDataEnd; /* One byte past the end of usable data */
@@ -298,16 +300,8 @@ struct MemPage {
DbPage *pDbPage; /* Pager page handle */
u16 (*xCellSize)(MemPage*,u8*); /* cellSizePtr method */
void (*xParseCell)(MemPage*,u8*,CellInfo*); /* btreeParseCell method */
Pgno pgno; /* Page number for this page */
};
/*
** The in-memory image of a disk page has the auxiliary information appended
** to the end. EXTRA_SIZE is the number of bytes of space needed to hold
** that extra information.
*/
#define EXTRA_SIZE sizeof(MemPage)
/*
** A linked list of the following structures is stored at BtShared.pLock.
** Locks are added (or upgraded from READ_LOCK to WRITE_LOCK) when a cursor