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mdbx: add key-making functions.

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Related to https://github.com/leo-yuriev/libmdbx/issues/76

Change-Id: I1edc8efd323af9adb53e6c2155e2ea39a1e575f4
This commit is contained in:
Leonid Yuriev
2020-01-22 03:43:09 +03:00
parent 700f3514b3
commit bf28856ac5
2 changed files with 162 additions and 5 deletions
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35
mdbx.h
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@@ -298,12 +298,12 @@
* - optimize (bulk) loading speed
* - (temporarily) reduce robustness to gain even more speed
* - gather statistics about the database
* - define custom sort orders
* - estimate size of range query result
* - double perfomance by LIFO reclaiming on storages with write-back
* - use sequences and canary markers
* - use lack-of-space callback (aka OOM-KICK)
* - use exclusive mode
* - define custom sort orders (but this is recommended to be avoided)
*
*
**** RESTRICTIONS & CAVEATS ***************************************************
@@ -2466,9 +2466,6 @@ typedef int(MDBX_cmp_func)(const MDBX_val *a, const MDBX_val *b);
* In contrast to LMDB, the MDBX allow this function to be called from multiple
* concurrent transactions or threads in the same process.
*
* Legacy mdbx_dbi_open() correspond to calling mdbx_dbi_open_ex() with the null
* keycmp and datacmp arguments.
*
* To use named database (with name != NULL), mdbx_env_set_maxdbs()
* must be called before opening the environment. Table names are
* keys in the internal unnamed database, and may be read but not written.
@@ -2509,10 +2506,19 @@ typedef int(MDBX_cmp_func)(const MDBX_val *a, const MDBX_val *b);
* Create the named database if it doesn't exist. This option is not
* allowed in a read-only transaction or a read-only environment.
*
* [out] dbi Address where the new MDBX_dbi handle will be stored.
*
* For mdbx_dbi_open_ex() additional arguments allow you to set custom
* comparison functions for keys and values (for multimaps).
* However, I recommend not using custom comparison functions, but instead
* converting the keys to one of the forms that are suitable for built-in
* comparators. The main reason for this is that you can't use mdbx_chk tools
* with a custom comparators. For instance take look to the mdbx_key_from_xxx()
* functions.
*
* [in] keycmp Optional custom key comparison function for a database.
* [in] datacmp Optional custom data comparison function for a database, takes
* effect only if database was opened with the MDB_DUPSORT flag.
* [out] dbi Address where the new MDBX_dbi handle will be stored.
*
* Returns A non-zero error value on failure and 0 on success, some
* possible errors are:
@@ -2530,6 +2536,25 @@ LIBMDBX_API int mdbx_dbi_open_ex(MDBX_txn *txn, const char *name,
LIBMDBX_API int mdbx_dbi_open(MDBX_txn *txn, const char *name, unsigned flags,
MDBX_dbi *dbi);
/* Key-making functions to avoid custom comparators.
*
* The mdbx_key_from_jsonInteger() build key which are comparable with
* keys created by mdbx_key_from_double(). So this allow mix int64 and IEEE754
* double values in one index for JSON-numbers with restriction for integer
* numbers range corresponding to RFC-7159 (i.e. [-(2**53)+1, (2**53)-1].
* See bottom of page 6 at https://tools.ietf.org/html/rfc7159 */
LIBMDBX_API uint64_t mdbx_key_from_jsonInteger(const int64_t json_integer);
LIBMDBX_API uint64_t mdbx_key_from_double(const double ieee754_64bit);
LIBMDBX_API uint64_t mdbx_key_from_ptrdouble(const double *const ieee754_64bit);
LIBMDBX_API uint32_t mdbx_key_from_float(const float ieee754_32bit);
LIBMDBX_API uint32_t mdbx_key_from_ptrfloat(const float *const ieee754_32bit);
__inline uint64_t mdbx_key_from_int64(const int64_t i64) {
return UINT64_C(0x8000000000000000) + i64;
}
__inline uint32_t mdbx_key_from_int32(const int32_t i32) {
return UINT32_C(0x80000000) + i32;
}
/* Retrieve statistics for a database.
*
* [in] txn A transaction handle returned by mdbx_txn_begin().