{"Entry":{"collection":"conn","key":"target-session-attrs","name":"target_session_attrs","aliases":["PGTARGETSESSIONATTRS","target_session_attrs"],"metadata":{"aliases":["PGTARGETSESSIONATTRS","target_session_attrs"],"category":"Connection destination","content_hash":"36300722f2e6d2ed355be886a54f817b625dcc468acbbf9b779010fbfec6828d","derived_content_hash":"2821966cdc5bb9e0e89f8d0ad486f3cacddbd7008204ead300e29a127e6c1c3a","documentation_refresh":{"batch":"20261113","original_source_rev":"","versions":{"14":"14.25","15":"15.20","16":"16.16","17":"17.12","18":"18.7","19":"19rc2"}},"imported_at":"2026-09-30T00:40:35.195573+08:00","name":"target_session_attrs","name_zh":"","slug":"target-session-attrs","summary":"This option determines whether the session must have certain properties to be acceptable. It's typically used in combination with multiple host names to select the first acceptable alternative among several hosts. There are six modes:"}},"Definition":{"Collection":"conn","Key":"target-session-attrs","SourceDatabase":"center","Version":"18","SourceTable":"connection_parameter","SourceKey":"target-session-attrs","SourceRevision":"ee8d1a3612338fd9adf250730cb640fcc5233b5491337cc00a316a44e3a0b9f8","Facts":{"comparison_data":{"compiled_default_expression":"DefaultTargetSessionAttrs","default_evidence":["session must accept read-write transactions by default (that is, the server must not be in hot standby mode and the default_transaction_read_only parameter must be off )","session must not accept read-write transactions by default (the converse)"],"definition":"This option determines whether the session must have certain properties to be acceptable. It's typically used in combination with multiple host names to select the first acceptable alternative among several hosts. There are six modes: any (default) any successful connection is acceptable read-write session must accept read-write transactions by default (that is, the server must not be in hot standby mode and the default_transaction_read_only parameter must be off ) read-only session must not accept read-write transactions by default (the converse) primary server must not be in hot standby mode standby server must be in hot standby mode prefer-standby first try to find a standby server, but if none of the listed hosts is a standby server, try again in any mode","documented":true,"environment":"PGTARGETSESSIONATTRS","keyword":"target_session_attrs"},"comparison_hash":"c66b8f5bf0ca0f898f8ff39c1588e0405c263592f5997098b467b8064bd9c45b","default_evidence":["session must accept read-write transactions by default (that is, the server must not be in hot standby mode and the default_transaction_read_only parameter must be off )","session must not accept read-write transactions by default (the converse)"],"description":["This option determines whether the session must have certain properties to be acceptable. It's typically used in combination with multiple host names to select the first acceptable alternative among several hosts. There are six modes:"],"description_zh":"这个选项确定会话是否必须具有某些属性才能被接受。通常与多个主机名结合使用，以便在多个主机中选择第一个可接受的候选项。有六种模式： any （默认） 任何成功的连接都是可接受的 read-write 会话必须默认接受读写事务（即，服务器不能处于热备模式，并且 default_transaction_read_only 参数必须为 off ） read-only 会话默认不接受读写事务（相反） primary 服务器不能处于热备模式 standby 服务器必须处于热备模式 prefer-standby 首先尝试找到一个备库，但如果列出的主机中没有一个是备库，则再次尝试 any 模式","description_zh_html":"\u003cp\u003e连接参数 target_session_attrs。\u003c/p\u003e\u003ch3\u003e同版本中文手册定义\u003c/h3\u003e\u003cdd\u003e\u003cp\u003e\n        这个选项确定会话是否必须具有某些属性才能被接受。通常与多个主机名结合使用，以便在多个主机中选择第一个可接受的候选项。有六种模式：\n\n        \u003c/p\u003e\u003cdiv class=\"variablelist\"\u003e\u003cdl class=\"variablelist\"\u003e\u003cdt\u003e\u003cspan class=\"term\"\u003e\u003ccode class=\"literal\"\u003eany\u003c/code\u003e（默认）\u003c/span\u003e\u003c/dt\u003e\u003cdd\u003e\u003cp\u003e\n            任何成功的连接都是可接受的\n           \u003c/p\u003e\u003c/dd\u003e\u003cdt\u003e\u003cspan class=\"term\"\u003e\u003ccode class=\"literal\"\u003eread-write\u003c/code\u003e\u003c/span\u003e \u003c/dt\u003e\u003cdd\u003e\u003cp\u003e\n            会话必须默认接受读写事务（即，服务器不能处于热备模式，并且 \u003ccode class=\"varname\"\u003edefault_transaction_read_only\u003c/code\u003e 参数必须为 \u003ccode class=\"literal\"\u003eoff\u003c/code\u003e）\n           \u003c/p\u003e\u003c/dd\u003e\u003cdt\u003e\u003cspan class=\"term\"\u003e\u003ccode class=\"literal\"\u003eread-only\u003c/code\u003e\u003c/span\u003e \u003c/dt\u003e\u003cdd\u003e\u003cp\u003e\n            会话默认不接受读写事务（相反）\n           \u003c/p\u003e\u003c/dd\u003e\u003cdt\u003e\u003cspan class=\"term\"\u003e\u003ccode class=\"literal\"\u003eprimary\u003c/code\u003e\u003c/span\u003e \u003c/dt\u003e\u003cdd\u003e\u003cp\u003e\n            服务器不能处于热备模式\n           \u003c/p\u003e\u003c/dd\u003e\u003cdt\u003e\u003cspan class=\"term\"\u003e\u003ccode class=\"literal\"\u003estandby\u003c/code\u003e\u003c/span\u003e \u003c/dt\u003e\u003cdd\u003e\u003cp\u003e\n            服务器必须处于热备模式\n           \u003c/p\u003e\u003c/dd\u003e\u003cdt\u003e\u003cspan class=\"term\"\u003e\u003ccode class=\"literal\"\u003eprefer-standby\u003c/code\u003e\u003c/span\u003e \u003c/dt\u003e\u003cdd\u003e\u003cp\u003e\n            首先尝试找到一个备库，但如果列出的主机中没有一个是备库，则再次尝试 \u003ccode class=\"literal\"\u003eany\u003c/code\u003e 模式\n           \u003c/p\u003e\u003c/dd\u003e\u003c/dl\u003e\u003c/div\u003e\u003cp\u003e\n\u003c/p\u003e\u003c/dd\u003e\u003cp\u003e\u003ca href=\"/zh/docs/18/libpq-connect.html#LIBPQ-CONNECT-TARGET-SESSION-ATTRS\"\u003e查看完整中文手册与上下文\u003c/a\u003e。\u003c/p\u003e","documented":true,"environment":[{"description":"PGTARGETSESSIONATTRS behaves the same as the target_session_attrs connection parameter.","name":"PGTARGETSESSIONATTRS","source_url":"/docs/18/libpq-envars.html"}],"facts":[{"label":"Client library","value":"libpq 18.6"},{"label":"Manual definition","value":"Documented"},{"label":"Source environment fallback","value":"PGTARGETSESSIONATTRS"},{"label":"Compiled fallback expression","value":"DefaultTargetSessionAttrs"}],"facts_zh":[{"label":"客户端库","value":"libpq 18.6"},{"label":"手册定义","value":"手册已记载"},{"label":"源码中的环境变量回退","value":"PGTARGETSESSIONATTRS"},{"label":"编译时回退表达式","value":"DefaultTargetSessionAttrs"}],"keyword":"target_session_attrs","manual_html":"\u003cdiv\u003e\u003cdl class=\"variablelist\"\u003e\u003cdt id=\"LIBPQ-CONNECT-TARGET-SESSION-ATTRS\"\u003e\u003cspan class=\"term\"\u003e\u003ccode class=\"literal\"\u003etarget_session_attrs\u003c/code\u003e\u003c/span\u003e \u003c/dt\u003e\u003cdd\u003e\n\u003cp\u003eThis option determines whether the session must have certain properties to be acceptable. 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These are useful to avoid hard-coding database connection information into simple client applications, for example.","Service names can be defined in either a per-user service file or a system-wide file. If the same service name exists in both the user and the system file, the user file takes precedence. By default, the per-user service file is named ~/.pg_service.conf . On Microsoft Windows, it is named %APPDATA%\\postgresql\\.pg_service.conf (where %APPDATA% refers to the Application Data subdirectory in the user's profile). A different file name can be specified by setting the environment variable PGSERVICEFILE . The system-wide file is named pg_service.conf . By default it is sought in the etc directory of the PostgreSQL installation (use pg_config --sysconfdir to identify this directory precisely). Another directory, but not a different file name, can be specified by setting the environment variable PGSYSCONFDIR .","Connection parameters obtained from a service file are combined with parameters obtained from other sources. A service file setting overrides the corresponding environment variable, and in turn can be overridden by a value given directly in the connection string. 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These are useful to avoid hard-coding database connection information into simple client applications, for example.","Service names can be defined in either a per-user service file or a system-wide file. If the same service name exists in both the user and the system file, the user file takes precedence. By default, the per-user service file is named ~/.pg_service.conf . On Microsoft Windows, it is named %APPDATA%\\postgresql\\.pg_service.conf (where %APPDATA% refers to the Application Data subdirectory in the user's profile). A different file name can be specified by setting the environment variable PGSERVICEFILE . The system-wide file is named pg_service.conf . By default it is sought in the etc directory of the PostgreSQL installation (use pg_config --sysconfdir to identify this directory precisely). Another directory, but not a different file name, can be specified by setting the environment variable PGSYSCONFDIR .","Connection parameters obtained from a service file are combined with parameters obtained from other sources. A service file setting overrides the corresponding environment variable, and in turn can be overridden by a value given directly in the connection string. For example, using the above service file, a connection string service=mydb port=5434 will use host somehost , port 5434 , user admin , and other parameters as set by environment variables or built-in defaults."],"title":"Default resolution and service-file precedence"},{"paragraphs":["PGTARGETSESSIONATTRS behaves the same as the target_session_attrs connection parameter."],"title":"Environment variable evidence"}],"sections_zh":[{"paragraphs":["以下环境变量可用于选择连接参数的默认值，供 PQconnectdb 、 PQsetdbLogin 和 PQsetdb 在调用代码未直接指定参数值时使用。例如，这样可以避免在简单的客户端应用程序中硬编码数据库连接信息。","服务名称可以在每个用户的服务文件或系统范围的文件中定义。如果同一个服务名称存在于用户文件和系统文件中，则用户文件优先。默认情况下，每个用户的服务文件名为 ~/.pg_service.conf 。在Microsoft Windows上，它的名称为 %APPDATA%\\postgresql\\.pg_service.conf （其中 %APPDATA% 指用户配置文件夹中的应用数据子目录）。可以通过设置环境变量 PGSERVICEFILE 来指定不同的文件名。系统范围的文件名为 pg_service.conf 。默认情况下，在 PostgreSQL 安装的 etc 目录中寻找（使用 pg_config --sysconfdir 来准确识别此目录）。可以通过设置环境变量 PGSYSCONFDIR 来指定另一个目录，但不能指定不同的文件名。","从服务文件中获取的连接参数会与其他来源的参数合并。服务文件中的设置会覆盖相应的环境变量，而连接字符串中直接给出的值又会覆盖服务文件中的设置。例如，使用上述服务文件时，连接字符串 service=mydb port=5434 将使用主机 somehost 、端口 5434 、用户 admin ，以及由环境变量或内置默认值设置的其他参数。"],"title":"默认值解析与服务文件优先级"},{"paragraphs":["PGTARGETSESSIONATTRS 的行为与 target_session_attrs 连接参数相同。"],"title":"环境变量证据"}],"signature":"target_session_attrs","source_option":{"compiled_default_expression":"DefaultTargetSessionAttrs","declaration":"\"target_session_attrs\", \"PGTARGETSESSIONATTRS\", DefaultTargetSessionAttrs, NULL, \"Target-Session-Attrs\", \"\", 15, offsetof(struct pg_conn, target_session_attrs)","environment":"PGTARGETSESSIONATTRS","keyword":"target_session_attrs","source_notes":[]},"sources":[{"anchor":"LIBPQ-CONNECT-TARGET-SESSION-ATTRS","file":"libpq-connect.html","label":"18.6 English manual · 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declarations","sha256":"44a6e386cbfd67ebe768d6ef5493098119c2e6b4796239d53e5ed7b122b206a5","url":"https://ftp.postgresql.org/pub/source/v18.6/postgresql-18.6.tar.bz2"},{"anchor":"","file":"libpq-envars.html","label":"18.6 English manual · libpq-envars.html","sha256":"d64db73f3d48127bb984a5f775e77b7bcca2ba4bd218333cf24a45fcdd7c4363","url":"/docs/18/libpq-envars.html"},{"anchor":"","file":"libpq-pgservice.html","label":"18.6 English manual · libpq-pgservice.html","sha256":"6035a3f0ee1d0fd80db5bf58834390b884eecd23206659bdf6f07560deea5aa7","url":"/docs/18/libpq-pgservice.html"}]},"MeasuredEvidence":{}},"Text":{"Collection":"conn","Key":"target-session-attrs","SourceDatabase":"center","Version":"18","Locale":"en","Title":"target_session_attrs","Summary":"This option determines whether the session must have certain properties to be acceptable. It's typically used in combination with multiple host names to select the first acceptable alternative among several hosts. There are six modes:","BodyHTML":"\u003cdiv\u003e\u003cdl\u003e\u003cdt id=\"LIBPQ-CONNECT-TARGET-SESSION-ATTRS\"\u003e\u003cspan\u003e\u003ccode\u003etarget_session_attrs\u003c/code\u003e\u003c/span\u003e \u003c/dt\u003e\u003cdd\u003e\n\u003cp\u003eThis option determines whether the session must have certain properties to be acceptable. It\u0026#39;s typically used in combination with multiple host names to select the first acceptable alternative among several hosts. There are six modes:\u003c/p\u003e\n\u003cdiv\u003e\n\u003cdl\u003e\n\u003cdt\u003e\u003cspan\u003e\u003ccode\u003eany\u003c/code\u003e (default)\u003c/span\u003e\u003c/dt\u003e\n\u003cdd\u003e\n\u003cp\u003eany successful connection is acceptable\u003c/p\u003e\n\u003c/dd\u003e\n\u003cdt\u003e\u003cspan\u003e\u003ccode\u003eread-write\u003c/code\u003e\u003c/span\u003e\u003c/dt\u003e\n\u003cdd\u003e\n\u003cp\u003esession must accept read-write transactions by default (that is, the server must not be in hot standby mode and the \u003ccode\u003edefault_transaction_read_only\u003c/code\u003e parameter must be \u003ccode\u003eoff\u003c/code\u003e)\u003c/p\u003e\n\u003c/dd\u003e\n\u003cdt\u003e\u003cspan\u003e\u003ccode\u003eread-only\u003c/code\u003e\u003c/span\u003e\u003c/dt\u003e\n\u003cdd\u003e\n\u003cp\u003esession must not accept read-write transactions by default (the converse)\u003c/p\u003e\n\u003c/dd\u003e\n\u003cdt\u003e\u003cspan\u003e\u003ccode\u003eprimary\u003c/code\u003e\u003c/span\u003e\u003c/dt\u003e\n\u003cdd\u003e\n\u003cp\u003eserver must not be in hot standby mode\u003c/p\u003e\n\u003c/dd\u003e\n\u003cdt\u003e\u003cspan\u003e\u003ccode\u003estandby\u003c/code\u003e\u003c/span\u003e\u003c/dt\u003e\n\u003cdd\u003e\n\u003cp\u003eserver must be in hot standby mode\u003c/p\u003e\n\u003c/dd\u003e\n\u003cdt\u003e\u003cspan\u003e\u003ccode\u003eprefer-standby\u003c/code\u003e\u003c/span\u003e\u003c/dt\u003e\n\u003cdd\u003e\n\u003cp\u003efirst try to find a standby server, but if none of the listed hosts is a standby server, try again in \u003ccode\u003eany\u003c/code\u003e mode\u003c/p\u003e\n\u003c/dd\u003e\n\u003c/dl\u003e\n\u003c/div\u003e\n\u003c/dd\u003e\u003c/dl\u003e\u003c/div\u003e","SourceRevision":"ee8d1a3612338fd9adf250730cb640fcc5233b5491337cc00a316a44e3a0b9f8","ContentHash":"14f25d1e3d332c903070f43f33a515ca56319d769552e4ca4f774920fe4b9ac2","Payload":{"description":["This option determines whether the session must have certain properties to be acceptable. It's typically used in combination with multiple host names to select the first acceptable alternative among several hosts. There are six modes:"],"manual_html":"\u003cdiv\u003e\u003cdl class=\"variablelist\"\u003e\u003cdt id=\"LIBPQ-CONNECT-TARGET-SESSION-ATTRS\"\u003e\u003cspan class=\"term\"\u003e\u003ccode class=\"literal\"\u003etarget_session_attrs\u003c/code\u003e\u003c/span\u003e \u003c/dt\u003e\u003cdd\u003e\n\u003cp\u003eThis option determines whether the session must have certain properties to be acceptable. It's typically used in combination with multiple host names to select the first acceptable alternative among several hosts. There are six modes:\u003c/p\u003e\n\u003cdiv class=\"variablelist\"\u003e\n\u003cdl class=\"variablelist\"\u003e\n\u003cdt\u003e\u003cspan class=\"term\"\u003e\u003ccode class=\"literal\"\u003eany\u003c/code\u003e (default)\u003c/span\u003e\u003c/dt\u003e\n\u003cdd\u003e\n\u003cp\u003eany successful connection is acceptable\u003c/p\u003e\n\u003c/dd\u003e\n\u003cdt\u003e\u003cspan class=\"term\"\u003e\u003ccode class=\"literal\"\u003eread-write\u003c/code\u003e\u003c/span\u003e\u003c/dt\u003e\n\u003cdd\u003e\n\u003cp\u003esession must accept read-write transactions by default (that is, the server must not be in hot standby mode and the \u003ccode class=\"varname\"\u003edefault_transaction_read_only\u003c/code\u003e parameter must be \u003ccode class=\"literal\"\u003eoff\u003c/code\u003e)\u003c/p\u003e\n\u003c/dd\u003e\n\u003cdt\u003e\u003cspan class=\"term\"\u003e\u003ccode class=\"literal\"\u003eread-only\u003c/code\u003e\u003c/span\u003e\u003c/dt\u003e\n\u003cdd\u003e\n\u003cp\u003esession must not accept read-write transactions by default (the converse)\u003c/p\u003e\n\u003c/dd\u003e\n\u003cdt\u003e\u003cspan class=\"term\"\u003e\u003ccode class=\"literal\"\u003eprimary\u003c/code\u003e\u003c/span\u003e\u003c/dt\u003e\n\u003cdd\u003e\n\u003cp\u003eserver must not be in hot standby mode\u003c/p\u003e\n\u003c/dd\u003e\n\u003cdt\u003e\u003cspan class=\"term\"\u003e\u003ccode class=\"literal\"\u003estandby\u003c/code\u003e\u003c/span\u003e\u003c/dt\u003e\n\u003cdd\u003e\n\u003cp\u003eserver must be in hot standby mode\u003c/p\u003e\n\u003c/dd\u003e\n\u003cdt\u003e\u003cspan class=\"term\"\u003e\u003ccode class=\"literal\"\u003eprefer-standby\u003c/code\u003e\u003c/span\u003e\u003c/dt\u003e\n\u003cdd\u003e\n\u003cp\u003efirst try to find a standby server, but if none of the listed hosts is a standby server, try again in \u003ccode class=\"literal\"\u003eany\u003c/code\u003e mode\u003c/p\u003e\n\u003c/dd\u003e\n\u003c/dl\u003e\n\u003c/div\u003e\n\u003c/dd\u003e\u003c/dl\u003e\u003c/div\u003e","related":[{"label":"Connection service file","url":"/docs/18/libpq-pgservice.html"},{"label":"Password file","url":"/docs/18/libpq-pgpass.html"},{"label":"All libpq environment variables","url":"/docs/18/libpq-envars.html"}],"sections":[{"paragraphs":["The following environment variables can be used to select default connection parameter values, which will be used by PQconnectdb , PQsetdbLogin and PQsetdb if no value is directly specified by the calling code. These are useful to avoid hard-coding database connection information into simple client applications, for example.","Service names can be defined in either a per-user service file or a system-wide file. If the same service name exists in both the user and the system file, the user file takes precedence. By default, the per-user service file is named ~/.pg_service.conf . On Microsoft Windows, it is named %APPDATA%\\postgresql\\.pg_service.conf (where %APPDATA% refers to the Application Data subdirectory in the user's profile). A different file name can be specified by setting the environment variable PGSERVICEFILE . The system-wide file is named pg_service.conf . By default it is sought in the etc directory of the PostgreSQL installation (use pg_config --sysconfdir to identify this directory precisely). Another directory, but not a different file name, can be specified by setting the environment variable PGSYSCONFDIR .","Connection parameters obtained from a service file are combined with parameters obtained from other sources. A service file setting overrides the corresponding environment variable, and in turn can be overridden by a value given directly in the connection string. For example, using the above service file, a connection string service=mydb port=5434 will use host somehost , port 5434 , user admin , and other parameters as set by environment variables or built-in defaults."],"title":"Default resolution and service-file precedence"},{"paragraphs":["PGTARGETSESSIONATTRS behaves the same as the target_session_attrs connection parameter."],"title":"Environment variable evidence"}],"tables":[{"columns":[{"key":"name","label":"Variable"},{"key":"description","label":"Documented behavior"}],"key":"environment","rows":[{"description":"PGTARGETSESSIONATTRS behaves the same as the target_session_attrs connection parameter.","name":{"text":"PGTARGETSESSIONATTRS","url":"/docs/18/libpq-envars.html"}}],"title":"Environment fallback"}]}},"RequestedLocale":"en","Fallback":false,"Versions":["10","11","12","13","14","15","16","17","18","19","20"],"Locales":["en","zh-Hans"],"Signatures":null,"Spellings":null,"SQLState":null,"Evidence":null}