Full_Name: James Rouzier Version: LMDB mdb.master OS: N/A URL: https://github.com/rouzier/openldap/commit/33f1dc8be4a8503e78930f130ff9c8e5aa9bfa7b Submission from: (NULL) (70.81.32.80) New feature inclusion request: "Context for compare functions" I am finishing up a new perl module which is a very thin wrapper for LMDB. (The current perl LMDB module does not fit my needs as it does not support NO_TLS really support). When looking at mdb_set_compare and mdb_set_dupsort. There were three choices. * Not support mdb_set_compare, mdb_set_dupsort in the module. * Capture each mdb_*(del|put|get) function to figure which dbi I am using. * Add support for contexts in the compare functions. So I decided on the latter. I understand that passing a context for each compare can add some overhead. So I made this feature optional it is only enabled if the macro MDB_CMP_CTX is enabled. This patch does the following. * Adds context to the MDB_cmp_func typedef int (MDB_cmp_func)(const MDB_val *a, const MDB_val *b ,void* ctx); * And two new data members to the MDB_dbx struct * void *md_cmpctx; /**< user-provided context for md_cmp */ * void *md_dcmpctx; /**< user-provided context for md_dcmp */ * Add functions for setting/getting the contexts * int mdb_set_cmpctx(MDB_txn *txn, MDB_dbi dbi, void *ctx); * int mdb_set_dcmpctx(MDB_txn *txn, MDB_dbi dbi, void *ctx); * int mdb_get_cmpctx(MDB_txn *txn, MDB_dbi dbi, void **ctx); * int mdb_get_dcmpctx(MDB_txn *txn, MDB_dbi dbi, void **ctx); I have no problem maintaining this as a separate patch if it does not fit in the vision of LMDB. I believe this can be useful for people who wants to add LMDB to a scripting language. New feature inclusion request: "Context for compare functions" I am finishing up a new perl module which is a very thin wrapper for LMDB. (The current perl LMDB module does not fit my needs as it does not support NO_TLS really well). When looking at mdb_set_compare and mdb_set_dupsort. There were three choices. * Not support mdb_set_compare, mdb_set_dupsort in the module. * Capture each mdb_*(del|put|get) function to figure which dbi I am using. * Add support for contexts in the compare functions. So I decided on the latter. I understand that passing a context for each compare can add some overhead. So I made this feature optional it is only enabled if the macro MDB_CMP_CTX is enabled. This patch does the following. * Adds context to the MDB_cmp_func typedef int (MDB_cmp_func)(const MDB_val *a, const MDB_val *b ,void* ctx); * And two new data members to the MDB_dbx struct * void *md_cmpctx; /**< user-provided context for md_cmp */ * void *md_dcmpctx; /**< user-provided context for md_dcmp */ * Add functions for setting/getting the contexts * int mdb_set_cmpctx(MDB_txn *txn, MDB_dbi dbi, void *ctx); * int mdb_set_dcmpctx(MDB_txn *txn, MDdbi i dbi, void *ctx); * int mdb_get_cmpctx(MDB_txn *txn, MDB_dbi dbi, void **ctx); * int mdb_get_dcmpctx(MDB_txn *txn, MDB_dbi dbi, void **ctx); I have no problem maintaining this as a separate patch if it does not fit in the vision of LMDB. I figured it might be very useful for others. Thank You for creating and releasing LMDB I, James Rouzier, hereby place the following modifications to OpenLDAP Software (and only these modifications) into the public domain. Hence, these modifications may be freely used and/or redistributed for any purpose with or without attribution and/or other notice.
rouzier@gmail.com wrote: > Full_Name: James Rouzier > Version: LMDB mdb.master > OS: N/A > URL: https://github.com/rouzier/openldap/commit/33f1dc8be4a8503e78930f130ff9c8e5aa9bfa7b > Submission from: (NULL) (70.81.32.80) > > > New feature inclusion request: "Context for compare functions" > > I am finishing up a new perl module which is a very thin wrapper for LMDB. > (The current perl LMDB module does not fit my needs as it does not support > NO_TLS really support). > > When looking at mdb_set_compare and mdb_set_dupsort. > > There were three choices. > > * Not support mdb_set_compare, mdb_set_dupsort in the module. > * Capture each mdb_*(del|put|get) function to figure which dbi I am using. > * Add support for contexts in the compare functions. > > So I decided on the latter. > > I understand that passing a context for each compare can add some overhead. > So I made this feature optional it is only enabled if the macro MDB_CMP_CTX is > enabled. I don't see supporting compare functions in interpreted languages being a realistic/worthwhile thing to do. The difference in performance is orders of magnitude. I also don't believe such conditional compilation is a good idea. LMDB is designed to be simple, to have very few options, and to Just Work the same on every platform. Conditionally compiled features are horrible because you can't guess which features will be present in a system-installed library. -- -- Howard Chu CTO, Symas Corp. http://www.symas.com Director, Highland Sun http://highlandsun.com/hyc/ Chief Architect, OpenLDAP http://www.openldap.org/project/
Howard thank you for taking the time to explain your reasoning. I am curious if I were remove the conditional compilation would the patch be more palatable. Because usually if you are using an interpreted language you are already taking a performance hit. Also it only slows your program down if you use the compare functions. If answer is still no I will just maintain the patch in my own branch. James Rouzier. On Sat, May 2, 2015 at 6:04 PM, Howard Chu <hyc@symas.com> wrote: > rouzier@gmail.com wrote: > >> Full_Name: James Rouzier >> Version: LMDB mdb.master >> OS: N/A >> URL: >> https://github.com/rouzier/openldap/commit/33f1dc8be4a8503e78930f130ff9c8e5aa9bfa7b >> Submission from: (NULL) (70.81.32.80) >> >> >> New feature inclusion request: "Context for compare functions" >> >> I am finishing up a new perl module which is a very thin wrapper for LMDB. >> (The current perl LMDB module does not fit my needs as it does not support >> NO_TLS really support). >> >> When looking at mdb_set_compare and mdb_set_dupsort. >> >> There were three choices. >> >> * Not support mdb_set_compare, mdb_set_dupsort in the module. >> * Capture each mdb_*(del|put|get) function to figure which dbi I am using. >> * Add support for contexts in the compare functions. >> >> So I decided on the latter. >> >> I understand that passing a context for each compare can add some >> overhead. >> So I made this feature optional it is only enabled if the macro >> MDB_CMP_CTX is >> enabled. >> > > I don't see supporting compare functions in interpreted languages being a > realistic/worthwhile thing to do. The difference in performance is orders > of magnitude. > > I also don't believe such conditional compilation is a good idea. LMDB is > designed to be simple, to have very few options, and to Just Work the same > on every platform. Conditionally compiled features are horrible because you > can't guess which features will be present in a system-installed library. > > -- > -- Howard Chu > CTO, Symas Corp. http://www.symas.com > Director, Highland Sun http://highlandsun.com/hyc/ > Chief Architect, OpenLDAP http://www.openldap.org/project/ >
*** This issue has been marked as a duplicate of issue 7980 ***