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ldb sometimes specify a string-append merge operator (#5607)

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Summary:
Right now, ldb cannot scan a DB with merge operands with default ldb. There is no hard to give a general merge operator so that it can at least print out something
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5607

Test Plan: Run ldb against a DB with merge operands and see the outputs.

Differential Revision: D16442634

fbshipit-source-id: c66c414ec07f219cfc6e6ec2cc14c783ee95df54
This commit is contained in:
sdong 2019-07-23 13:56:52 -07:00 committed by Facebook Github Bot
parent 112702ac6c
commit 3782accf7d
2 changed files with 15 additions and 0 deletions
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1
HISTORY.md
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@ -18,6 +18,7 @@
* Rate limited deletion of WALs is only enabled if DBOptions::wal_dir is not set, or explicitly set to db_name passed to DB::Open and DBOptions::db_paths is empty, or same as db_paths[0].path
* Overload GetAllKeyVersions() to support non-default column family.
* Added new APIs ExportColumnFamily() and CreateColumnFamilyWithImport() to support export and import of a Column Family. https://github.com/facebook/rocksdb/issues/3469
* ldb sometimes uses a string-append merge operator if no merge operator is passed in. This is to allow users to print keys from a DB with a merge operator.
### New Features
* Add an option `snap_refresh_nanos` (default to 0) to periodically refresh the snapshot list in compaction jobs. Assign to 0 to disable the feature.

14
tools/ldb_cmd.cc
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@ -31,6 +31,7 @@
#include "util/coding.h"
#include "util/stderr_logger.h"
#include "util/string_util.h"
#include "utilities/merge_operators.h"
#include "utilities/ttl/db_ttl_impl.h"
#include <cstdlib>
@ -353,11 +354,24 @@ void LDBCommand::OpenDB() {
stderr,
"wal_dir loaded from the option file doesn't exist. Ignore it.\n");
}
// If merge operator is not set, set a string append operator. There is
// no harm doing it.
for (auto& cf_entry : column_families_) {
if (!cf_entry.options.merge_operator) {
cf_entry.options.merge_operator =
MergeOperators::CreateStringAppendOperator(':');
}
}
}
options_ = PrepareOptionsForOpenDB();
if (!exec_state_.IsNotStarted()) {
return;
}
if (column_families_.empty() && !options_.merge_operator) {
// No harm to add a general merge operator if it is not specified.
options_.merge_operator = MergeOperators::CreateStringAppendOperator(':');
}
// Open the DB.
Status st;
std::vector<ColumnFamilyHandle*> handles_opened;