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mdbx: minor refine mdbx.h

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Change-Id: I5fee861582987cc11a648a3365b19c28e493317d
This commit is contained in:
Leonid Yuriev 2019-10-09 14:36:04 +03:00
parent 26641d839b
commit 1573d110f6
1 changed files with 16 additions and 10 deletions
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mdbx.h
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@ -722,8 +722,8 @@ void LIBMDBX_API NTAPI mdbx_dll_handler(PVOID module, DWORD reason,
/* Opaque structure for a database environment. /* Opaque structure for a database environment.
* *
* An environment supports multiple databases, all residing in the same * An environment supports multiple key-value databases (aka key-value spaces
* shared-memory map. */ * or tables), all residing in the same shared-memory map. */
typedef struct MDBX_env MDBX_env; typedef struct MDBX_env MDBX_env;
/* Opaque structure for a transaction handle. /* Opaque structure for a transaction handle.
@ -907,11 +907,20 @@ LIBMDBX_API char *mdbx_dump_val(const MDBX_val *key, char *const buf,
/* MDBX_WRITEMAP = map data into memory with write permission. /* MDBX_WRITEMAP = map data into memory with write permission.
* *
* Use a writeable memory map unless MDBX_RDONLY is set. This uses fewer mallocs * Use a writeable memory map unless MDBX_RDONLY is set. This uses fewer mallocs
* but loses protection from application bugs like wild pointer writes and other * and requires much less work for tracking database pages, but loses protection
* bad updates into the database. This may be slightly faster for DBs that fit * from application bugs like wild pointer writes and other bad updates into the
* entirely in RAM, but is slower for DBs larger than RAM. Also adds the * database. This may be slightly faster for DBs that fit entirely in RAM, but
* possibility for stray application writes thru pointers to silently corrupt * is slower for DBs larger than RAM. Also adds the possibility for stray
* the database. Incompatible with nested transactions. * application writes thru pointers to silently corrupt the database.
* Incompatible with nested transactions.
*
* NOTE: The MDBX_WRITEMAP mode is incompatible with nested transactions, since
* this is unreasonable. I.e. nested transactions requires mallocation of
* database pages and more work for tracking ones, which neuters a
* performance boost caused by the MDBX_WRITEMAP mode.
*
* NOTE: MDBX don't allow to mix processes with and without MDBX_WRITEMAP on
* the same environment. In such case MDBX_INCOMPATIBLE will be generated.
* *
* - with MDBX_WRITEMAP = all data will be mapped into memory in the read-write * - with MDBX_WRITEMAP = all data will be mapped into memory in the read-write
* mode. This offers a significant performance benefit, since the data will * mode. This offers a significant performance benefit, since the data will
@ -925,9 +934,6 @@ LIBMDBX_API char *mdbx_dump_val(const MDBX_val *key, char *const buf,
* mode. This requires stocking all modified database pages in memory and * mode. This requires stocking all modified database pages in memory and
* then writing them to disk through file operations. * then writing them to disk through file operations.
* *
* NOTE: MDBX don't allow to mix processes with and without MDBX_WRITEMAP on
* the same environment. In such case MDBX_INCOMPATIBLE will be generated.
*
* This flag affects only at environment opening but can't be changed after. */ * This flag affects only at environment opening but can't be changed after. */
#define MDBX_WRITEMAP 0x80000u #define MDBX_WRITEMAP 0x80000u