The following parameters are intended for developer testing, and
     should never be used on a production database.  However, some of
     them can be used to assist with the recovery of severely damaged
     databases.  As such, they have been excluded from the sample
     postgresql.conf file.  Note that many of these
     parameters require special source compilation flags to work at all.
    
allow_in_place_tablespaces (boolean)
      
      
        Allows tablespaces to be created as directories inside
        pg_tblspc, when an empty location string
        is provided to the CREATE TABLESPACE command.  This
        is intended to allow testing replication scenarios where primary and
        standby servers are running on the same machine.  Such directories
        are likely to confuse backup tools that expect to find only symbolic
        links in that location.
        Only superusers and users with the appropriate SET
        privilege can change this setting.
       
allow_system_table_mods (boolean)
      
      
        Allows modification of the structure of system tables as well as
        certain other risky actions on system tables.  This is otherwise not
        allowed even for superusers.  Ill-advised use of this setting can
        cause irretrievable data loss or seriously corrupt the database
        system.
        Only superusers and users with the appropriate SET
        privilege can change this setting.
       
backtrace_functions (string)
      
      This parameter contains a comma-separated list of C function names. If an error is raised and the name of the internal C function where the error happens matches a value in the list, then a backtrace is written to the server log together with the error message. This can be used to debug specific areas of the source code.
Backtrace support is not available on all platforms, and the quality of the backtraces depends on compilation options.
        Only superusers and users with the appropriate SET
        privilege can change this setting.
       
debug_discard_caches (integer)
      
      
        When set to 1, each system catalog cache entry is
        invalidated at the first possible opportunity, whether or not
        anything that would render it invalid really occurred.  Caching of
        system catalogs is effectively disabled as a result, so the server
        will run extremely slowly.  Higher values run the cache invalidation
        recursively, which is even slower and only useful for testing
        the caching logic itself.  The default value of 0
        selects normal catalog caching behavior.
       
        This parameter can be very helpful when trying to trigger
        hard-to-reproduce bugs involving concurrent catalog changes, but it
        is otherwise rarely needed.  See the source code files
        inval.c and
        pg_config_manual.h for details.
       
        This parameter is supported when
        DISCARD_CACHES_ENABLED was defined at compile time
        (which happens automatically when using the
        configure option
        --enable-cassert).  In production builds, its value
        will always be 0 and attempts to set it to another
        value will raise an error.
       
force_parallel_mode (enum)
      
      
        Allows the use of parallel queries for testing purposes even in cases
        where no performance benefit is expected.
        The allowed values of force_parallel_mode are
        off (use parallel mode only when it is expected to improve
        performance), on (force parallel query for all queries
        for which it is thought to be safe), and regress (like
        on, but with additional behavior changes as explained
        below).
       
        More specifically, setting this value to on will add
        a Gather node to the top of any query plan for which this
        appears to be safe, so that the query runs inside of a parallel worker.
        Even when a parallel worker is not available or cannot be used,
        operations such as starting a subtransaction that would be prohibited
        in a parallel query context will be prohibited unless the planner
        believes that this will cause the query to fail.  If failures or
        unexpected results occur when this option is set, some functions used
        by the query may need to be marked PARALLEL UNSAFE
        (or, possibly, PARALLEL RESTRICTED).
       
        Setting this value to regress has all of the same effects
        as setting it to on plus some additional effects that are
        intended to facilitate automated regression testing.  Normally,
        messages from a parallel worker include a context line indicating that,
        but a setting of regress suppresses this line so that the
        output is the same as in non-parallel execution.  Also,
        the Gather nodes added to plans by this setting are hidden
        in EXPLAIN output so that the output matches what
        would be obtained if this setting were turned off.
       
ignore_system_indexes (boolean)
      
      Ignore system indexes when reading system tables (but still update the indexes when modifying the tables). This is useful when recovering from damaged system indexes. This parameter cannot be changed after session start.
post_auth_delay (integer)
      
      The amount of time to delay when a new server process is started, after it conducts the authentication procedure. This is intended to give developers an opportunity to attach to the server process with a debugger. If this value is specified without units, it is taken as seconds. A value of zero (the default) disables the delay. This parameter cannot be changed after session start.
pre_auth_delay (integer)
      
      
        The amount of time to delay just after a
        new server process is forked, before it conducts the
        authentication procedure.  This is intended to give developers an
        opportunity to attach to the server process with a debugger to
        trace down misbehavior in authentication.
        If this value is specified without units, it is taken as seconds.
        A value of zero (the default) disables the delay.
        This parameter can only be set in the postgresql.conf
        file or on the server command line.
       
trace_notify (boolean)
      
      
        Generates a great amount of debugging output for the
        LISTEN and NOTIFY
        commands.  client_min_messages or
        log_min_messages must be
        DEBUG1 or lower to send this output to the
        client or server logs, respectively.
       
trace_recovery_messages (enum)
      
      
        Enables logging of recovery-related debugging output that otherwise
        would not be logged. This parameter allows the user to override the
        normal setting of log_min_messages, but only for
        specific messages. This is intended for use in debugging hot standby.
        Valid values are DEBUG5, DEBUG4,
        DEBUG3, DEBUG2, DEBUG1, and
        LOG.  The default, LOG, does not affect
        logging decisions at all.  The other values cause recovery-related
        debug messages of that priority or higher to be logged as though they
        had LOG priority; for common settings of
        log_min_messages this results in unconditionally sending
        them to the server log.
        This parameter can only be set in the postgresql.conf
        file or on the server command line.
       
trace_sort (boolean)
      
      
        If on, emit information about resource usage during sort operations.
        This parameter is only available if the TRACE_SORT macro
        was defined when PostgreSQL was compiled.
        (However, TRACE_SORT is currently defined by default.)
       
trace_locks (boolean)
      
      If on, emit information about lock usage. Information dumped includes the type of lock operation, the type of lock and the unique identifier of the object being locked or unlocked. Also included are bit masks for the lock types already granted on this object as well as for the lock types awaited on this object. For each lock type a count of the number of granted locks and waiting locks is also dumped as well as the totals. An example of the log file output is shown here:
LOG:  LockAcquire: new: lock(0xb7acd844) id(24688,24696,0,0,0,1)
      grantMask(0) req(0,0,0,0,0,0,0)=0 grant(0,0,0,0,0,0,0)=0
      wait(0) type(AccessShareLock)
LOG:  GrantLock: lock(0xb7acd844) id(24688,24696,0,0,0,1)
      grantMask(2) req(1,0,0,0,0,0,0)=1 grant(1,0,0,0,0,0,0)=1
      wait(0) type(AccessShareLock)
LOG:  UnGrantLock: updated: lock(0xb7acd844) id(24688,24696,0,0,0,1)
      grantMask(0) req(0,0,0,0,0,0,0)=0 grant(0,0,0,0,0,0,0)=0
      wait(0) type(AccessShareLock)
LOG:  CleanUpLock: deleting: lock(0xb7acd844) id(24688,24696,0,0,0,1)
      grantMask(0) req(0,0,0,0,0,0,0)=0 grant(0,0,0,0,0,0,0)=0
      wait(0) type(INVALID)
        Details of the structure being dumped may be found in
        src/include/storage/lock.h.
       
        This parameter is only available if the LOCK_DEBUG
        macro was defined when PostgreSQL was
        compiled.
       
trace_lwlocks (boolean)
      
      If on, emit information about lightweight lock usage. Lightweight locks are intended primarily to provide mutual exclusion of access to shared-memory data structures.
        This parameter is only available if the LOCK_DEBUG
        macro was defined when PostgreSQL was
        compiled.
       
trace_userlocks (boolean)
      
      
        If on, emit information about user lock usage.  Output is the same
        as for trace_locks, only for advisory locks.
       
        This parameter is only available if the LOCK_DEBUG
        macro was defined when PostgreSQL was
        compiled.
       
trace_lock_oidmin (integer)
      
      If set, do not trace locks for tables below this OID (used to avoid output on system tables).
        This parameter is only available if the LOCK_DEBUG
        macro was defined when PostgreSQL was
        compiled.
       
trace_lock_table (integer)
      
      Unconditionally trace locks on this table (OID).
        This parameter is only available if the LOCK_DEBUG
        macro was defined when PostgreSQL was
        compiled.
       
debug_deadlocks (boolean)
      
      If set, dumps information about all current locks when a deadlock timeout occurs.
        This parameter is only available if the LOCK_DEBUG
        macro was defined when PostgreSQL was
        compiled.
       
log_btree_build_stats (boolean)
      
      If set, logs system resource usage statistics (memory and CPU) on various B-tree operations.
        This parameter is only available if the BTREE_BUILD_STATS
        macro was defined when PostgreSQL was
        compiled.
       
wal_consistency_checking (string)
      
      This parameter is intended to be used to check for bugs in the WAL redo routines. When enabled, full-page images of any buffers modified in conjunction with the WAL record are added to the record. If the record is subsequently replayed, the system will first apply each record and then test whether the buffers modified by the record match the stored images. In certain cases (such as hint bits), minor variations are acceptable, and will be ignored. Any unexpected differences will result in a fatal error, terminating recovery.
        The default value of this setting is the empty string, which disables
        the feature.  It can be set to all to check all
        records, or to a comma-separated list of resource managers to check
        only records originating from those resource managers.  Currently,
        the supported resource managers are heap,
        heap2, btree, hash,
        gin, gist, sequence,
        spgist, brin, and generic.
        Extensions may define additional resource managers. Only superusers and users with
        the appropriate SET privilege can change this setting.
       
wal_debug (boolean)
      
      
        If on, emit WAL-related debugging output. This parameter is
        only available if the WAL_DEBUG macro was
        defined when PostgreSQL was
        compiled.
       
ignore_checksum_failure (boolean)
      
      Only has effect if data checksums are enabled.
        Detection of a checksum failure during a read normally causes
        PostgreSQL to report an error, aborting the current
        transaction.  Setting ignore_checksum_failure to on causes
        the system to ignore the failure (but still report a warning), and
        continue processing.  This behavior may cause crashes, propagate
        or hide corruption, or other serious problems.  However, it may allow
        you to get past the error and retrieve undamaged tuples that might still be
        present in the table if the block header is still sane. If the header is
        corrupt an error will be reported even if this option is enabled. The
        default setting is off.
        Only superusers and users with the appropriate SET
        privilege can change this setting.
       
zero_damaged_pages (boolean)
      
      
        Detection of a damaged page header normally causes
        PostgreSQL to report an error, aborting the current
        transaction.  Setting zero_damaged_pages to on causes
        the system to instead report a warning, zero out the damaged
        page in memory, and continue processing.  This behavior will destroy data,
        namely all the rows on the damaged page.  However, it does allow you to get
        past the error and retrieve rows from any undamaged pages that might
        be present in the table.  It is useful for recovering data if
        corruption has occurred due to a hardware or software error.  You should
        generally not set this on until you have given up hope of recovering
        data from the damaged pages of a table.  Zeroed-out pages are not
        forced to disk so it is recommended to recreate the table or
        the index before turning this parameter off again.  The
        default setting is off.
        Only superusers and users with the appropriate SET
        privilege can change this setting.
       
ignore_invalid_pages (boolean)
      
      
        If set to off (the default), detection of
        WAL records having references to invalid pages during
        recovery causes PostgreSQL to
        raise a PANIC-level error, aborting the recovery. Setting
        ignore_invalid_pages to on
        causes the system to ignore invalid page references in WAL records
        (but still report a warning), and continue the recovery.
        This behavior may cause crashes, data loss,
        propagate or hide corruption, or other serious problems.
        However, it may allow you to get past the PANIC-level error,
        to finish the recovery, and to cause the server to start up.
        The parameter can only be set at server start. It only has effect
        during recovery or in standby mode.
       
jit_debugging_support (boolean)
      
      
        If LLVM has the required functionality, register generated functions
        with GDB.  This makes debugging easier.
        The default setting is off.
        This parameter can only be set at server start.
       
jit_dump_bitcode (boolean)
      
      
        Writes the generated LLVM IR out to the
        file system, inside data_directory. This is only
        useful for working on the internals of the JIT implementation.
        The default setting is off.
        Only superusers and users with the appropriate SET
        privilege can change this setting.
       
jit_expressions (boolean)
      
      
        Determines whether expressions are JIT compiled, when JIT compilation
        is activated (see Section 32.2).  The default is
        on.
       
jit_profiling_support (boolean)
      
      
        If LLVM has the required functionality, emit the data needed to allow
        perf to profile functions generated by JIT.
        This writes out files to ~/.debug/jit/; the
        user is responsible for performing cleanup when desired.
        The default setting is off.
        This parameter can only be set at server start.
       
jit_tuple_deforming (boolean)
      
      
        Determines whether tuple deforming is JIT compiled, when JIT
        compilation is activated (see Section 32.2).
        The default is on.
       
remove_temp_files_after_crash (boolean)
      
      
        When set to on, which is the default,
        PostgreSQL will automatically remove
        temporary files after a backend crash. If disabled, the files will be
        retained and may be used for debugging, for example. Repeated crashes
        may however result in accumulation of useless files. This parameter
        can only be set in the postgresql.conf file or on
        the server command line.