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mdbx-doc: more for custom comparators.

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Change-Id: I3326c5bdedbbdb01b1865bff68aa7ba8bc7056cc
This commit is contained in:
Leonid Yuriev 2020-03-02 13:50:33 +03:00
parent 8358dda7f1
commit 251d34d6e6
2 changed files with 10 additions and 4 deletions
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11
mdbx.h
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@ -2590,9 +2590,14 @@ typedef int(MDBX_cmp_func)(const MDBX_val *a, const MDBX_val *b);
* 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.
* comparators (for instance take look to the mdbx_key_from_xxx()
* functions). The reasons to not using custom comparators are:
* - The order of records could not be validated without your code.
* So mdbx_chk utility will reports "wrong order" errors
* and the '-i' option is required to ignore ones.
* - A records could not be ordered or sorted without your code.
* So mdbx_load utility should be used with '-a' option to preserve
* input data order.
*
* [in] keycmp Optional custom key comparison function for a database.
* [in] datacmp Optional custom data comparison function for a database, takes

3
src/tools/mdbx_load.c
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@ -339,7 +339,8 @@ static void usage(void) {
"dbpath\n"
" -V\t\tprint version and exit\n"
" -q\t\tbe quiet\n"
" -a\t\tappend records in input order\n"
" -a\t\tappend records in input order (required for custom "
"comparators)\n"
" -f file\tread from file instead of stdin\n"
" -s name\tload into named subDB\n"
" -N\t\tuse NOOVERWRITE on puts\n"