20.17. Developer Options

20.17. Developer Options
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+ 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. +