PostgreSQL 常用维护操作（三）

 PostgreSQL配置文件的修改方法：

1. 配置文件所在路径：

[postgres@kevin data]$ pwd /opt/postgresql/data [postgres@kevin data]$ ll 总用量 1332 drwx------ 8 postgres dba 4096 7月 13 10:50 base drwx------ 2 postgres dba 4096 7月 19 03:42 global -rw------- 1 postgres dba 1181357 7月 17 16:17 gmon.out drwx------ 159 postgres dba 4096 7月 19 03:44 gprof drwx------ 2 postgres dba 4096 7月 9 09:42 pg_clog -rw------- 1 postgres dba 3755 7月 9 14:54 pg_hba.conf -rw------- 1 postgres dba 1631 7月 9 09:42 pg_ident.conf drwx------ 4 postgres dba 4096 7月 9 09:42 pg_multixact drwx------ 2 postgres dba 4096 7月 19 05:57 pg_stat_tmp drwx------ 2 postgres dba 4096 7月 9 09:42 pg_subtrans drwx------ 2 postgres dba 4096 7月 13 10:54 pg_tblspc drwx------ 2 postgres dba 4096 7月 9 09:42 pg_twophase -rw------- 1 postgres dba 4 7月 9 09:42 PG_VERSION drwx------ 3 postgres dba 4096 7月 9 09:42 pg_xlog -rw------- 1 postgres dba 16837 7月 9 14:52 postgresql.conf -rw------- 1 postgres dba 16815 7月 9 14:51 postgresql.conf_duanyx_bak -rw------- 1 postgres dba 29 7月 19 03:42 postmaster.opts -rw------- 1 postgres dba 46 7月 19 03:42 postmaster.pid [postgres@kevin data]$

2. SQL方式修改，可以在运行时设置，当然只有于部分选项，使用方法如下：

kevin_test=# SET work_mem = '16MB'; SET kevin_test=# kevin_test=# SELECT * FROM pg_settings WHERE source = 'session'; -[ RECORD 1 ]------------------------------------------------------------------- -------------------------------------------------- name | work_mem setting | 16384 unit | kB category | Resource Usage / Memory short_desc | Sets the maximum memory to be used for query workspaces. extra_desc | This much memory can be used by each internal sort operation and ha sh table before switching to temporary disk files. context | user vartype | integer source | session min_val | 64 max_val | 2097151 enumvals | boot_val | 1024 reset_val | 1024 sourcefile | sourceline | kevin_test=#

恢复默认设置的方法：

kevin_test=# RESET work_mem; RESET kevin_test=# SELECT * FROM pg_settings WHERE name = 'work_mem'; -[ RECORD 1 ]--------------------------------------------------------------------------------------------------------------------- name | work_mem setting | 1024 unit | kB category | Resource Usage / Memory short_desc | Sets the maximum memory to be used for query workspaces. extra_desc | This much memory can be used by each internal sort operation and hash table before switching to temporary disk files. context | user vartype | integer source | default min_val | 64 max_val | 2097151 enumvals | boot_val | 1024 reset_val | 1024 sourcefile | sourceline | kevin_test=#

3.查看配置项的值，当然你可以看接查看postgre.conf文件的内容，不过最好使用SQL方法查看和修改，更为快速，当然你要先知道要查看的选项的名称。

kevin_test=# SHOW work_mem; work_mem ---------- 1MB (1 row) kevin_test=#

补充一下，如果确实不知道选项的名了，可以先查一下，这些均存储在pg_settings表中，呵呵，PostgreSQL的一个特点就在这，所有数据均由数据库自己维护。

kevin_test=# SELECT name, short_desc FROM pg_settings; name | short_desc ---------------------------------+---------------------------------------------------------------------------------------------------------------------------- --- add_missing_from | Automatically adds missing table references to FROM clauses. allow_system_table_mods | Allows modifications of the structure of system tables. archive_command | Sets the shell command that will be called to archive a WAL file. archive_mode | Allows archiving of WAL files using archive_command. archive_timeout | Forces a switch to the next xlog file if a new file has not been started within N seconds. array_nulls | Enable input of NULL elements in arrays. authentication_timeout | Sets the maximum allowed time to complete client authentication. autovacuum | Starts the autovacuum subprocess. autovacuum_analyze_scale_factor | Number of tuple inserts, updates or deletes prior to analyze as a fraction of reltuples. autovacuum_analyze_threshold | Minimum number of tuple inserts, updates or deletes prior to analyze. autovacuum_freeze_max_age | Age at which to autovacuum a table to prevent transaction ID wraparound. autovacuum_max_workers | Sets the maximum number of simultaneously running autovacuum worker processes. autovacuum_naptime | Time to sleep between autovacuum runs. autovacuum_vacuum_cost_delay | Vacuum cost delay in milliseconds, for autovacuum. autovacuum_vacuum_cost_limit | Vacuum cost amount available before napping, for autovacuum. autovacuum_vacuum_scale_factor | Number of tuple updates or deletes prior to vacuum as a fraction of reltuples. autovacuum_vacuum_threshold | Minimum number of tuple updates or deletes prior to vacuum. backslash_quote | Sets whether "\'" is allowed in string literals. bgwriter_delay | Background writer sleep time between rounds. bgwriter_lru_maxpages | Background writer maximum number of LRU pages to flush per round. bgwriter_lru_multiplier | Multiple of the average buffer usage to free per round. block_size | Shows the size of a disk block. bonjour_name | Sets the Bonjour broadcast service name. check_function_bodies | Check function bodies during CREATE FUNCTION. checkpoint_completion_target | Time spent flushing dirty buffers during checkpoint, as fraction of checkpoint interval. checkpoint_segments | Sets the maximum distance in log segments between automatic WAL checkpoints. checkpoint_timeout | Sets the maximum time between automatic WAL checkpoints. checkpoint_warning | Enables warnings if checkpoint segments are filled more frequently than this. client_encoding | Sets the client's character set encoding. client_min_messages | Sets the message levels that are sent to the client. commit_delay | Sets the delay in microseconds between transaction commit and flushing WAL to disk. commit_siblings | Sets the minimum concurrent open transactions before performing commit_delay. config_file | Sets the server's main configuration file. constraint_exclusion | Enables the planner to use constraints to optimize queries. cpu_index_tuple_cost | Sets the planner's estimate of the cost of processing each index entry during an index scan. cpu_operator_cost | Sets the planner's estimate of the cost of processing each operator or function call. cpu_tuple_cost | Sets the planner's estimate of the cost of processing each tuple (row). cursor_tuple_fraction | Sets the planner's estimate of the fraction of a cursor's rows that will be retrieved. custom_variable_classes | Sets the list of known custom variable classes. data_directory | Sets the server's data directory. DateStyle | Sets the display format for date and time values. db_user_namespace | Enables per-database user names. deadlock_timeout | Sets the time to wait on a lock before checking for deadlock. debug_assertions | Turns on various assertion checks. debug_pretty_print | Indents parse and plan tree displays. debug_print_parse | Logs each query's parse tree. debug_print_plan | Logs each query's execution plan. debug_print_rewritten | Logs each query's rewritten parse tree. default_statistics_target | Sets the default statistics target. default_tablespace | Sets the default tablespace to create tables and indexes in. default_text_search_config | Sets default text search configuration. default_transaction_isolation | Sets the transaction isolation level of each new transaction. default_transaction_read_only | Sets the default read-only status of new transactions. default_with_oids | Create new tables with OIDs by default. dynamic_library_path | Sets the path for dynamically loadable modules. effective_cache_size | Sets the planner's assumption about the size of the disk cache. effective_io_concurrency | Number of simultaneous requests that can be handled efficiently by the disk subsystem. enable_bitmapscan | Enables the planner's use of bitmap-scan plans. enable_hashagg | Enables the planner's use of hashed aggregation plans. enable_hashjoin | Enables the planner's use of hash join plans. enable_indexscan | Enables the planner's use of index-scan plans. enable_mergejoin | Enables the planner's use of merge join plans. enable_nestloop | Enables the planner's use of nested-loop join plans. enable_seqscan | Enables the planner's use of sequential-scan plans. enable_sort | Enables the planner's use of explicit sort steps. enable_tidscan | Enables the planner's use of TID scan plans. escape_string_warning | Warn about backslash escapes in ordinary string literals. external_pid_file | Writes the postmaster PID to the specified file. extra_float_digits | Sets the number of digits displayed for floating-point values. from_collapse_limit | Sets the FROM-list size beyond which subqueries are not collapsed. fsync | Forces synchronization of updates to disk. full_page_writes | Writes full pages to WAL when first modified after a checkpoint. geqo | Enables genetic query optimization. geqo_effort | GEQO: effort is used to set the default for other GEQO parameters. geqo_generations | GEQO: number of iterations of the algorithm. geqo_pool_size | GEQO: number of individuals in the population. geqo_selection_bias | GEQO: selective pressure within the population. geqo_threshold | Sets the threshold of FROM items beyond which GEQO is used. gin_fuzzy_search_limit | Sets the maximum allowed result for exact search by GIN. hba_file | Sets the server's "hba" configuration file. ident_file | Sets the server's "ident" configuration file. ignore_system_indexes | Disables reading from system indexes. integer_datetimes | Datetimes are integer based. IntervalStyle | Sets the display format for interval values. join_collapse_limit | Sets the FROM-list size beyond which JOIN constructs are not flattened. krb_caseins_users | Sets whether Kerberos and GSSAPI user names should be treated as case-insensitive. krb_server_keyfile | Sets the location of the Kerberos server key file. krb_srvname | Sets the name of the Kerberos service. lc_collate | Shows the collation order locale. lc_ctype | Shows the character classification and case conversion locale. lc_messages | Sets the language in which messages are displayed. lc_monetary | Sets the locale for formatting monetary amounts. lc_numeric | Sets the locale for formatting numbers. lc_time | Sets the locale for formatting date and time values. listen_addresses | Sets the host name or IP address(es) to listen to. local_preload_libraries | Lists shared libraries to preload into each backend. log_autovacuum_min_duration | Sets the minimum execution time above which autovacuum actions will be logged. log_checkpoints | Logs each checkpoint. log_connections | Logs each successful connection. log_destination | Sets the destination for server log output. log_directory | Sets the destination directory for log files. log_disconnections | Logs end of a session, including duration. log_duration | Logs the duration of each completed SQL statement. log_error_verbosity | Sets the verbosity of logged messages. log_executor_stats | Writes executor performance statistics to the server log. log_filename | Sets the file name pattern for log files. log_hostname | Logs the host name in the connection logs. log_line_prefix | Controls information prefixed to each log line. log_lock_waits | Logs long lock waits. log_min_duration_statement | Sets the minimum execution time above which statements will be logged. log_min_error_statement | Causes all statements generating error at or above this level to be logged. log_min_messages | Sets the message levels that are logged. log_parser_stats | Writes parser performance statistics to the server log. log_planner_stats | Writes planner performance statistics to the server log. log_rotation_age | Automatic log file rotation will occur after N minutes. log_rotation_size | Automatic log file rotation will occur after N kilobytes. log_statement | Sets the type of statements logged. log_statement_stats | Writes cumulative performance statistics to the server log. log_temp_files | Log the use of temporary files larger than this number of kilobytes. log_timezone | Sets the time zone to use in log messages. log_truncate_on_rotation | Truncate existing log files of same name during log rotation. logging_collector | Start a subprocess to capture stderr output and/or csvlogs into log files. maintenance_work_mem | Sets the maximum memory to be used for maintenance operations. max_connections | Sets the maximum number of concurrent connections. max_files_per_process | Sets the maximum number of simultaneously open files for each server process. max_function_args | Shows the maximum number of function arguments. max_identifier_length | Shows the maximum identifier length. max_index_keys | Shows the maximum number of index keys. max_locks_per_transaction | Sets the maximum number of locks per transaction. max_prepared_transactions | Sets the maximum number of simultaneously prepared transactions. max_stack_depth | Sets the maximum stack depth, in kilobytes. password_encryption | Encrypt passwords. port | Sets the TCP port the server listens on. post_auth_delay | Waits N seconds on connection startup after authentication. pre_auth_delay | Waits N seconds on connection startup before authentication. random_page_cost | Sets the planner's estimate of the cost of a nonsequentially fetched disk page. regex_flavor | Sets the regular expression "flavor". search_path | Sets the schema search order for names that are not schema-qualified. segment_size | Shows the number of pages per disk file. seq_page_cost | Sets the planner's estimate of the cost of a sequentially fetched disk page. server_encoding | Sets the server (database) character set encoding. server_version | Shows the server version. server_version_num | Shows the server version as an integer. session_replication_role | Sets the session's behavior for triggers and rewrite rules. shared_buffers | Sets the number of shared memory buffers used by the server. shared_preload_libraries | Lists shared libraries to preload into server. silent_mode | Runs the server silently. sql_inheritance | Causes subtables to be included by default in various commands. ssl | Enables SSL connections. standard_conforming_strings | Causes '...' strings to treat backslashes literally. statement_timeout | Sets the maximum allowed duration of any statement. stats_temp_directory | Writes temporary statistics files to the specified directory. superuser_reserved_connections | Sets the number of connection slots reserved for superusers. synchronize_seqscans | Enable synchronized sequential scans. synchronous_commit | Sets immediate fsync at commit. syslog_facility | Sets the syslog "facility" to be used when syslog enabled. syslog_ident | Sets the program name used to identify PostgreSQL messages in syslog. tcp_keepalives_count | Maximum number of TCP keepalive retransmits. tcp_keepalives_idle | Time between issuing TCP keepalives. tcp_keepalives_interval | Time between TCP keepalive retransmits. temp_buffers | Sets the maximum number of temporary buffers used by each session. temp_tablespaces | Sets the tablespace(s) to use for temporary tables and sort files. TimeZone | Sets the time zone for displaying and interpreting time stamps. timezone_abbreviations | Selects a file of time zone abbreviations. trace_notify | Generates debugging output for LISTEN and NOTIFY. trace_sort | Emit information about resource usage in sorting. track_activities | Collects information about executing commands. track_activity_query_size | Sets the size reserved for pg_stat_activity.current_query, in bytes. track_counts | Collects statistics on database activity. track_functions | Collects function-level statistics on database activity. transaction_isolation | Sets the current transaction's isolation level. transaction_read_only | Sets the current transaction's read-only status. transform_null_equals | Treats "expr=NULL" as "expr IS NULL". unix_socket_directory | Sets the directory where the Unix-domain socket will be created. unix_socket_group | Sets the owning group of the Unix-domain socket. unix_socket_permissions | Sets the access permissions of the Unix-domain socket. update_process_title | Updates the process title to show the active SQL command. vacuum_cost_delay | Vacuum cost delay in milliseconds. vacuum_cost_limit | Vacuum cost amount available before napping. vacuum_cost_page_dirty | Vacuum cost for a page dirtied by vacuum. vacuum_cost_page_hit | Vacuum cost for a page found in the buffer cache. vacuum_cost_page_miss | Vacuum cost for a page not found in the buffer cache. vacuum_freeze_min_age | Minimum age at which VACUUM should freeze a table row. vacuum_freeze_table_age | Age at which VACUUM should scan whole table to freeze tuples. wal_block_size | Shows the block size in the write ahead log. wal_buffers | Sets the number of disk-page buffers in shared memory for WAL. wal_segment_size | Shows the number of pages per write ahead log segment. wal_sync_method | Selects the method used for forcing WAL updates to disk. wal_writer_delay | WAL writer sleep time between WAL flushes. work_mem | Sets the maximum memory to be used for query workspaces. xmlbinary | Sets how binary values are to be encoded in XML. xmloption | Sets whether XML data in implicit parsing and serialization operations is to be considered as documents or content fragment s. zero_damaged_pages | Continues processing past damaged page headers. (193 rows) kevin_test=#

4.记住选项值的改动并不一定对整个数据库生效，有时仅对当前session在效，在执行SET语句时，可通过LOCAL选项明确指定。

kevin_test=# SET LOCAL work_mem='16MB'; SET kevin_test=#

5.查看系统中哪些选项被修改过。

kevin_test=# SELECT name, source, setting FROM pg_settings WHERE source != 'default' AND source != 'override' ORDER BY 2, 1; name | source | setting ----------------------------+----------------------+------------------- log_timezone | command line | PRC TimeZone | command line | PRC timezone_abbreviations | command line | Default DateStyle | configuration file | ISO, YMD default_text_search_config | configuration file | pg_catalog.simple lc_messages | configuration file | zh_CN.UTF-8 lc_monetary | configuration file | zh_CN.UTF-8 lc_numeric | configuration file | zh_CN.UTF-8 lc_time | configuration file | zh_CN.UTF-8 listen_addresses | configuration file | * max_connections | configuration file | 100 shared_buffers | configuration file | 3584 max_stack_depth | environment variable | 2048 (13 rows) kevin_test=#