DBCache.mesa
Last Edited by: MBrown on November 24, 1982 1:04 pm
Last Edited by: Wert, August 4, 1984 7:48:55 pm PDT
DIRECTORY
DBCommon USING [DBPage];
DBCache: DEFINITIONS
= BEGIN
Types
A CacheHandle represents an association between a database page and a core page. This association is guaranteed while the page is "locked", but may be broken at other times. Access to a page is more efficient if the CacheHandle is known in addition to the DBPage address, since hashing is avoided.
CacheHandle: TYPE = REF CacheRecord;
CacheRecord: PRIVATE TYPE = RECORD
[
dbPage: DBCommon.DBPage,
database page number
pagePtr: LONG POINTER,
location of the cache page in memory
lockCount: [0..7777B] ← 0,
incremented by read page, write page; decremented by unlock page. If >0, page will not move in core or leave cache.
occupied: BOOL ← FALSE,
true if this page contains valid data (is contained in ht).
written: BOOL ← FALSE,
true if this page has been written, needs to be stored back to file system.
readonly: BOOL ← FALSE,
true iff this page cannot be written (according to the file system).
pred: CacheHandle,
succ: CacheHandle,
Doubly-linked list of cache handles, used to maintain LRU information.
hashChain: CacheHandle
Singly-linked list of cache handles, used to resolve hash table collisions.
];
Procedures
END.
CHANGE LOG
Created by MBrown on January 4, 1980 2:21 PM
Adopted in meeting of 4 January; DBCacheDefs and DBFileDefs replace the former DBCacheDefs.
Changed by Suzuki on January 14, 1980 2:29 PM
Suffixes Defs are deleted
Changed by Suzuki on January 16, 1980 8:18 AM
EnumBRLockProc, RelRLockProc, and ObtainDBPage are added.
Changed by Suzuki on January 17, 1980 1:12 PM
WriteoutCache returns TRUE if write can succeed else returns FALSE.
Changed by Suzuki on February 8, 1980 4:28 PM
added NewPage and WriteLockedPage.
Changed by MBrown on February 21, 1980 2:32 PM
Made WriteLockedPage return no result. Added comment to NewPage that the contents of the page are unpredictable.
Changed by MBrown on February 21, 1980 10:36 PM
Added LockCountOfPage.
Changed by Suzuki on April 16, 1980 4:00 PM
Added LockCount and ObtainCoreLoc. Deleted LockCountOfPage.
Changed by MBrown on April 20, 1980 4:58 PM
Changed the pHint parm of LockCount and ObtainCoreLoc to pValidHint, to emphasize that they must be valid for these procs to work.
Changed by MBrown on August 23, 1980 6:20 PM
Added CheckState to the interface.
Changed by MBrown on September 3, 1980 10:03 PM
CacheHandle is now an opaque type. Eliminated dependency on ServerPineDefs by making lfh be an untyped pointer for now.
Changed by MBrown on September 12, 1980 11:15 AM
Added Finalize.
Changed by MBrown on September 18, 1980 3:11 PM
Made CacheHandle a LONG POINTER.
Changed by MBrown on February 27, 1981 11:19 AM
Flushed all of the stuff relating to broken read locks.
Changed by MBrown on August 6, 1982 2:43 pm
CacheHandle is a REF.
Changed by MBrown on November 24, 1982 1:04 pm
CacheRecord is concrete here; all procs are eliminated, as we are merging the cache and segment implementations.
Changed by Wert on August 4, 1984 7:48:20 pm PDT
Added tioga formatting.