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Comment clarifications in wal.c.

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FossilOrigin-Name: a029be10172e2e6a2ef4e3eb2ea1bd0ca85b16ed
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drh
2010-05-18 12:56:50 +00:00
parent 69c4696784
commit e730fec883
3 changed files with 15 additions and 21 deletions
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16
src/wal.c
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@@ -22,7 +22,7 @@
** WRITE-AHEAD LOG (WAL) FILE FORMAT
**
** A wal file consists of a header followed by zero or more "frames".
** The header is 12 bytes in size and consists of the following three
** The file header is 12 bytes in size and consists of the following three
** big-endian 32-bit unsigned integer values:
**
** 0: Database page size,
@@ -44,9 +44,9 @@
/*
** WAL-INDEX FILE FORMAT
**
** The wal-index file consists of a 32-byte header region, followed by an
** The wal-index consists of a 32-byte header region, followed by an
** 8-byte region that contains no useful data (used to apply byte-range locks
** to), followed by the data region.
** in some implementations), followed by the data region.
**
** The contents of both the header and data region are specified in terms
** of 1, 2 and 4 byte unsigned integers. All integers are stored in
@@ -57,19 +57,13 @@
** mapping from database page number to the set of locations in the wal
** file that contain versions of the database page. When a database
** client needs to read a page of data, it first queries the wal-index
** file to determine if the required version of the page is stored in
** to determine if the required version of the page is stored in
** the wal. If so, the page is read from the wal. If not, the page is
** read from the database file.
**
** Whenever a transaction is appended to the wal or a checkpoint transfers
** data from the wal into the database file, the wal-index is
** updated accordingly.
**
** The fields in the wal-index file header are described in the comment
** directly above the definition of struct WalIndexHdr (see below).
** Immediately following the fields in the WalIndexHdr structure is
** an 8 byte checksum based on the contents of the header. This field is
** not the same as the iCheck1 and iCheck2 fields of the WalIndexHdr.
*/
/* Object declarations */
@@ -1397,7 +1391,7 @@ int sqlite3WalFrames(
}
assert( pWal->pWiData==0 );
/* Append data to the log summary. It is not necessary to lock the
/* Append data to the wal-index. It is not necessary to lock the
** wal-index to do this as the RESERVED lock held on the db file
** guarantees that there are no other writers, and no data that may
** be in use by existing readers is being overwritten.