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mdbx: add mdbx_txn_info().
Change-Id: I7bef500c23899874c996694b7cc52a38366730f0
This commit is contained in:
parent
0b500798df
commit
83fbcb660f
65
mdbx.h
65
mdbx.h
@ -2048,6 +2048,69 @@ LIBMDBX_API int mdbx_env_set_assert(MDBX_env *env, MDBX_assert_func *func);
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LIBMDBX_API int mdbx_txn_begin(MDBX_env *env, MDBX_txn *parent, unsigned flags,
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MDBX_txn **txn);
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/* Information about the transaction */
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typedef struct MDBX_txn_info {
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uint64_t txn_id; /* The ID of the transaction. For a READ-ONLY transaction,
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this corresponds to the snapshot being read. */
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uint64_t
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txn_reader_lag; /* For READ-ONLY transaction: the lag from a recent
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MVCC-snapshot, i.e. the number of committed
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transaction since read transaction started.
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For WRITE transaction (provided if scan_rlt=true): the
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lag of the oldest reader from current transaction (i.e.
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atleast 1 if any reader running). */
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uint64_t txn_space_used; /* Used space by this transaction, i.e. corresponding
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to the last used database page. */
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uint64_t txn_space_limit_soft; /* Current size of database file. */
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uint64_t
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txn_space_limit_hard; /* Upper bound for size the database file,
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i.e. the value "size_upper" argument of the
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approriate call of mdbx_env_set_geometry(). */
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uint64_t txn_space_retired; /* For READ-ONLY transaction: The total size of
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the database pages that were retired by
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committed write transactions after the reader's
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MVCC-snapshot, i.e. the space which would be
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freed after the Reader releases the
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MVCC-snapshot for reuse by completion read
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transaction.
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For WRITE transaction: The summarized size of
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the database pages that were retired for now
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due Copy-On-Write during this transaction. */
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uint64_t
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txn_space_leftover; /* For READ-ONLY transaction: the space available for
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writer(s) and that must be exhausted for reason to
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call the OOM-killer for this read transaction.
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For WRITE transaction: the space inside transaction
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that left to MDBX_TXN_FULL error. */
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uint64_t
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txn_space_dirty; /* For READ-ONLY transaction (provided if scan_rlt=true):
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The retired distance for next more recent reader, i.e.
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the space that actually become available for reuse
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when only this transaction will be finished. For WRITE
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transaction: The summarized size of the dirty database
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pages that generated during this transaction. */
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} MDBX_txn_info;
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/* Return information about the MDBX transaction.
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*
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* [in] txn A transaction handle returned by mdbx_txn_begin().
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* [out] stat The address of an MDBX_txn_info structure
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* where the information will be copied.
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* [in[ scan_rlt The boolean flag controls the scan of the read lock table to
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* provide complete information. Such scan is relatively
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* expensive and you can avoid it if corresponding fields are
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* not needed (see description of MDBX_txn_info above).
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*
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* Returns A non-zero error value on failure and 0 on success. */
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LIBMDBX_API int mdbx_txn_info(MDBX_txn *txn, MDBX_txn_info *info, int scan_rlt);
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/* Returns the transaction's MDBX_env
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*
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* [in] txn A transaction handle returned by mdbx_txn_begin() */
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@ -2059,7 +2122,7 @@ LIBMDBX_API MDBX_env *mdbx_txn_env(MDBX_txn *txn);
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*
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* [in] txn A transaction handle returned by mdbx_txn_begin()
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*
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* Returns A transaction flags, valid if input is an active transaction,
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* Returns A transaction flags, valid if input is an valid transaction,
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* otherwise -1. */
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LIBMDBX_API int mdbx_txn_flags(MDBX_txn *txn);
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@ -3903,8 +3903,115 @@ int mdbx_txn_begin(MDBX_env *env, MDBX_txn *parent, unsigned flags,
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return rc;
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}
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int mdbx_txn_info(MDBX_txn *txn, MDBX_txn_info *info, int scan_rlt) {
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int rc = check_txn(txn, MDBX_TXN_BLOCKED - MDBX_TXN_HAS_CHILD);
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if (unlikely(rc != MDBX_SUCCESS))
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return rc;
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if (unlikely(!info))
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return MDBX_EINVAL;
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MDBX_env *const env = txn->mt_env;
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#if MDBX_TXN_CHECKPID
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if (unlikely(env->me_pid != mdbx_getpid())) {
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env->me_flags |= MDBX_FATAL_ERROR;
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return MDBX_PANIC;
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}
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#endif /* MDBX_TXN_CHECKPID */
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info->txn_id = txn->mt_txnid;
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info->txn_space_used = pgno2bytes(env, txn->mt_geo.next);
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if (txn->mt_flags & MDBX_RDONLY) {
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const MDBX_meta *head_meta;
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txnid_t head_txnid;
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uint64_t head_retired;
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do {
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/* fetch info from volatile head */
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head_meta = mdbx_meta_head(env);
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head_txnid = mdbx_meta_txnid_fluid(env, head_meta);
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head_retired = head_meta->mm_pages_retired;
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info->txn_space_limit_soft = pgno2bytes(env, head_meta->mm_geo.now);
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info->txn_space_limit_hard = pgno2bytes(env, head_meta->mm_geo.upper);
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info->txn_space_leftover =
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pgno2bytes(env, head_meta->mm_geo.now - head_meta->mm_geo.next);
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mdbx_compiler_barrier();
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} while (unlikely(head_meta != mdbx_meta_head(env) ||
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head_txnid != mdbx_meta_txnid_fluid(env, head_meta)));
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info->txn_reader_lag = head_txnid - info->txn_id;
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info->txn_space_dirty = info->txn_space_retired = 0;
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if (txn->mt_ro_reader &&
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head_retired > txn->mt_ro_reader->mr_snapshot_pages_retired) {
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info->txn_space_dirty = info->txn_space_retired = pgno2bytes(
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env, (pgno_t)(head_retired -
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txn->mt_ro_reader->mr_snapshot_pages_retired));
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MDBX_lockinfo *const lck = env->me_lck;
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if (scan_rlt && info->txn_reader_lag > 1 && lck) {
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/* find next more recent reader */
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txnid_t next_reader = head_txnid;
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const unsigned snap_nreaders = lck->mti_numreaders;
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for (unsigned i = 0; i < snap_nreaders; ++i) {
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retry:
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if (lck->mti_readers[i].mr_pid) {
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mdbx_jitter4testing(true);
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const txnid_t snap_txnid = lck->mti_readers[i].mr_txnid;
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const uint64_t snap_retired =
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lck->mti_readers[i].mr_snapshot_pages_retired;
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mdbx_compiler_barrier();
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if (unlikely(snap_txnid != lck->mti_readers[i].mr_txnid ||
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snap_retired !=
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lck->mti_readers[i].mr_snapshot_pages_retired))
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goto retry;
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if (snap_txnid > txn->mt_txnid && snap_txnid < next_reader) {
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next_reader = snap_txnid;
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info->txn_space_dirty = pgno2bytes(
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env, (pgno_t)(snap_retired -
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txn->mt_ro_reader->mr_snapshot_pages_retired));
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}
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}
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}
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}
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}
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} else {
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info->txn_space_limit_soft = pgno2bytes(env, txn->mt_geo.now);
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info->txn_space_limit_hard = pgno2bytes(env, txn->mt_geo.upper);
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info->txn_space_retired =
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pgno2bytes(env, MDBX_PNL_SIZE(txn->mt_retired_pages));
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info->txn_space_leftover = pgno2bytes(env, txn->mt_dirtyroom);
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info->txn_space_dirty =
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pgno2bytes(env, MDBX_DPL_TXNFULL - txn->mt_dirtyroom);
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info->txn_reader_lag = INT64_MAX;
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MDBX_lockinfo *const lck = env->me_lck;
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if (scan_rlt && lck) {
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txnid_t oldest_snapshot = txn->mt_txnid;
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const unsigned snap_nreaders = lck->mti_numreaders;
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if (snap_nreaders) {
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oldest_snapshot = mdbx_find_oldest(txn);
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if (oldest_snapshot == txn->mt_txnid - 1) {
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/* check if there is at least one reader */
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bool exists = false;
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for (unsigned i = 0; i < snap_nreaders; ++i) {
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if (lck->mti_readers[i].mr_pid &&
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txn->mt_txnid > lck->mti_readers[i].mr_txnid) {
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exists = true;
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break;
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}
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}
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oldest_snapshot += !exists;
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}
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}
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info->txn_reader_lag = txn->mt_txnid - oldest_snapshot;
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}
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}
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return MDBX_SUCCESS;
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}
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MDBX_env *mdbx_txn_env(MDBX_txn *txn) {
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if (unlikely(!txn || txn->mt_signature != MDBX_MT_SIGNATURE))
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if (unlikely(!txn || txn->mt_signature != MDBX_MT_SIGNATURE ||
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txn->mt_env->me_signature != MDBX_ME_SIGNATURE))
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return NULL;
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return txn->mt_env;
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}
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@ -3918,7 +4025,6 @@ uint64_t mdbx_txn_id(MDBX_txn *txn) {
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int mdbx_txn_flags(MDBX_txn *txn) {
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if (unlikely(!txn || txn->mt_signature != MDBX_MT_SIGNATURE))
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return -1;
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return txn->mt_flags;
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}
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