{"Entry":{"collection":"conn","key":"max-protocol-version","name":"max_protocol_version","aliases":["PGMAXPROTOCOLVERSION","max_protocol_version"],"metadata":{"aliases":["PGMAXPROTOCOLVERSION","max_protocol_version"],"category":"Session and protocol","content_hash":"518281880876a1fdcf00158ba0e62dea5de770297b6015e5067f963d3ff31453","derived_content_hash":"39775edd187a94b50dd8e956424ef79cba7ad9e5c91a6e5155f8152823195d03","documentation_refresh":{"batch":"20261113","original_source_rev":"","versions":{"18":"18.7","19":"19rc2"}},"imported_at":"2026-09-30T00:40:34.972986+08:00","name":"max_protocol_version","name_zh":"","slug":"max-protocol-version","summary":"Specifies the protocol version to request from the server. The default is to use version 3.0 of the PostgreSQL protocol, unless the connection string specifies a feature that relies on a higher protocol version, in which case the latest version supported by libpq is used. If the server does not support the protocol version requested by the client, the connection is automatically downgraded to a lower minor protocol version that the server supports. After the connection attempt has completed you can use PQfullProtocolVersion to find out which exact protocol version was negotiated."}},"Definition":{"Collection":"conn","Key":"max-protocol-version","SourceDatabase":"center","Version":"18","SourceTable":"connection_parameter","SourceKey":"max-protocol-version","SourceRevision":"ee8d1a3612338fd9adf250730cb640fcc5233b5491337cc00a316a44e3a0b9f8","Facts":{"comparison_data":{"compiled_default_expression":"NULL","default_evidence":["Specifies the protocol version to request from the server. The default is to use version 3.0 of the PostgreSQL protocol, unless the connection string specifies a feature that relies on a higher protocol version, in which case the latest version supported by libpq is used. If the server does not support the protocol version requested by the client, the connection is automatically downgraded to a lower minor protocol version that the server supports. After the connection attempt has completed you can use PQfullProtocolVersion to find out which exact protocol version was negotiated."],"definition":"Specifies the protocol version to request from the server. The default is to use version 3.0 of the PostgreSQL protocol, unless the connection string specifies a feature that relies on a higher protocol version, in which case the latest version supported by libpq is used. If the server does not support the protocol version requested by the client, the connection is automatically downgraded to a lower minor protocol version that the server supports. After the connection attempt has completed you can use PQfullProtocolVersion to find out which exact protocol version was negotiated. The current supported values are 3.0 , 3.2 , and latest . The latest value is equivalent to the latest protocol version supported by the libpq version being used, which is currently 3.2 .","documented":true,"environment":"PGMAXPROTOCOLVERSION","keyword":"max_protocol_version"},"comparison_hash":"5f247a227834da03d50d6864a46fa9fbd0be14445f495d2c8bfed4a4933ec304","default_evidence":["Specifies the protocol version to request from the server. The default is to use version 3.0 of the PostgreSQL protocol, unless the connection string specifies a feature that relies on a higher protocol version, in which case the latest version supported by libpq is used. If the server does not support the protocol version requested by the client, the connection is automatically downgraded to a lower minor protocol version that the server supports. After the connection attempt has completed you can use PQfullProtocolVersion to find out which exact protocol version was negotiated."],"description":["Specifies the protocol version to request from the server. The default is to use version 3.0 of the PostgreSQL protocol, unless the connection string specifies a feature that relies on a higher protocol version, in which case the latest version supported by libpq is used. If the server does not support the protocol version requested by the client, the connection is automatically downgraded to a lower minor protocol version that the server supports. After the connection attempt has completed you can use PQfullProtocolVersion to find out which exact protocol version was negotiated."],"description_zh":"这个参数指定要向服务器请求的协议版本。默认会使用 PostgreSQL 协议的 3.0 版本；但如果连接字符串指定了依赖更高协议版本的特性，则会使用 libpq 支持的最新版本。如果服务器不支持客户端请求的协议版本，连接会自动降级为服务器支持的较低次版本协议。连接尝试完成后，你可以使用 PQfullProtocolVersion 来确定最终协商得到的确切协议版本。 当前支持的值是 3.0 、 3.2 和 latest 。 latest 等价于正在使用的 libpq 版本所支持的最新协议版本，目前即 3.2 。","description_zh_html":"\u003cp\u003e连接参数 max_protocol_version。\u003c/p\u003e\u003ch3\u003e同版本中文手册定义\u003c/h3\u003e\u003cdd\u003e\u003cp\u003e\n        这个参数指定要向服务器请求的协议版本。默认会使用\n        \u003cspan class=\"productname\"\u003ePostgreSQL\u003c/span\u003e 协议的 \u003ccode class=\"literal\"\u003e3.0\u003c/code\u003e 版本；但如果连接字符串指定了依赖更高协议版本的特性，则会使用\n        \u003cspan class=\"application\"\u003elibpq\u003c/span\u003e 支持的最新版本。如果服务器不支持客户端请求的协议版本，连接会自动降级为服务器支持的较低次版本协议。连接尝试完成后，你可以使用 \u003ca class=\"xref\" href=\"/zh/docs/18/libpq-status.html#LIBPQ-PQFULLPROTOCOLVERSION\"\u003e\u003ccode class=\"function\"\u003ePQfullProtocolVersion\u003c/code\u003e\u003c/a\u003e 来确定最终协商得到的确切协议版本。\n       \u003c/p\u003e\u003cp\u003e\n        当前支持的值是 \u003ccode class=\"literal\"\u003e3.0\u003c/code\u003e、\u003ccode class=\"literal\"\u003e3.2\u003c/code\u003e\n        和 \u003ccode class=\"literal\"\u003elatest\u003c/code\u003e。\u003ccode class=\"literal\"\u003elatest\u003c/code\u003e 等价于正在使用的 \u003cspan class=\"application\"\u003elibpq\u003c/span\u003e 版本所支持的最新协议版本，目前即 \u003ccode class=\"literal\"\u003e3.2\u003c/code\u003e。\n       \u003c/p\u003e\u003c/dd\u003e\u003cp\u003e\u003ca href=\"/zh/docs/18/libpq-connect.html#LIBPQ-CONNECT-MAX-PROTOCOL-VERSION\"\u003e查看完整中文手册与上下文\u003c/a\u003e。\u003c/p\u003e","documented":true,"environment":[{"description":"PGMAXPROTOCOLVERSION behaves the same as the max_protocol_version connection parameter.","name":"PGMAXPROTOCOLVERSION","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":"PGMAXPROTOCOLVERSION"},{"label":"Compiled fallback expression","value":"NULL"}],"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":"PGMAXPROTOCOLVERSION"},{"label":"编译时回退表达式","value":"NULL"}],"keyword":"max_protocol_version","manual_html":"\u003cdiv\u003e\u003cdl class=\"variablelist\"\u003e\u003cdt id=\"LIBPQ-CONNECT-MAX-PROTOCOL-VERSION\"\u003e\u003cspan class=\"term\"\u003e\u003ccode class=\"literal\"\u003emax_protocol_version\u003c/code\u003e\u003c/span\u003e \u003c/dt\u003e\u003cdd\u003e\n\u003cp\u003eSpecifies the protocol version to request from the server. The default is to use version \u003ccode class=\"literal\"\u003e3.0\u003c/code\u003e of the \u003cspan class=\"productname\"\u003ePostgreSQL\u003c/span\u003e protocol, unless the connection string specifies a feature that relies on a higher protocol version, in which case the latest version supported by libpq is used. If the server does not support the protocol version requested by the client, the connection is automatically downgraded to a lower minor protocol version that the server supports. After the connection attempt has completed you can use \u003ca class=\"xref\" href=\"/docs/18/libpq-status.html#LIBPQ-PQFULLPROTOCOLVERSION\"\u003e\u003ccode class=\"function\"\u003ePQfullProtocolVersion\u003c/code\u003e\u003c/a\u003e to find out which exact protocol version was negotiated.\u003c/p\u003e\n\u003cp\u003eThe current supported values are \u003ccode class=\"literal\"\u003e3.0\u003c/code\u003e, \u003ccode class=\"literal\"\u003e3.2\u003c/code\u003e, and \u003ccode class=\"literal\"\u003elatest\u003c/code\u003e. The \u003ccode class=\"literal\"\u003elatest\u003c/code\u003e value is equivalent to the latest protocol version supported by the libpq version being used, which is currently \u003ccode class=\"literal\"\u003e3.2\u003c/code\u003e.\u003c/p\u003e\n\u003c/dd\u003e\u003c/dl\u003e\u003c/div\u003e","manual_path":"libpq-connect.html#LIBPQ-CONNECT-MAX-PROTOCOL-VERSION","precedence_evidence":["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."],"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"}],"release":{"channel":"stable","evidence_kind":"English manual and source declarations","label":"18.6","major":"18","manifest":{"index":"index.html","major":"18","pages":1148,"pdf":{"A4":{"built_at":"2026-09-26","bytes":15865106,"pages":3154,"sha256":"19512c405da53f9f7fcf0abba359223aa65f021be025bf3411381918f92e3190","url":"/files/documentation/pdf/18/postgresql-18-A4.pdf"},"US":{"built_at":"2026-09-26","bytes":15748059,"pages":3328,"sha256":"facbe6c229e598b872d3d98bef53308f46e06746006fa4590de9a7de9dd46319","url":"/files/documentation/pdf/18/postgresql-18-US.pdf"}},"release":"18.6","source_mode":"en SGML built with pinned official archive","source_sha256":"555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f","source_url":"https://ftp.postgresql.org/pub/source/v18.6/postgresql-18.6.tar.bz2","svg_assets":3,"tree":"18"},"ref":"https://ftp.postgresql.org/pub/source/v18.6/postgresql-18.6.tar.bz2","revision":"ee8d1a3612338fd9adf250730cb640fcc5233b5491337cc00a316a44e3a0b9f8","source_sha256":"555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"},"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":["PGMAXPROTOCOLVERSION behaves the same as the max_protocol_version 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":["PGMAXPROTOCOLVERSION 的行为与 max_protocol_version 连接参数相同。"],"title":"环境变量证据"}],"signature":"max_protocol_version","source_option":{"compiled_default_expression":"NULL","declaration":"\"max_protocol_version\", \"PGMAXPROTOCOLVERSION\", NULL, NULL, \"Max-Protocol-Version\", \"\", 6, offsetof(struct pg_conn, max_protocol_version)","environment":"PGMAXPROTOCOLVERSION","keyword":"max_protocol_version","source_notes":[]},"sources":[{"anchor":"LIBPQ-CONNECT-MAX-PROTOCOL-VERSION","file":"libpq-connect.html","label":"18.6 English manual · 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连接参数相同。","name":{"text":"PGMAXPROTOCOLVERSION","url":"/docs/18/libpq-envars.html"}}],"title":"环境变量回退"}],"zh_from":{"authored_translation":"source-derived-identity","body_sha256":"b0e3259b7738307dec34a27bb3ceac9f87f65186eeb76c0660f18ca326deee0e","kind":"same-version-chinese-manual-with-source-derived-identity","manual":{"anchor":"LIBPQ-CONNECT-MAX-PROTOCOL-VERSION","build_id":107,"extraction":"exact-definition","fragment_sha256":"da1aa3e414f19b22a66a11bc7464ed7734603793776b5ee84b1e72c6aa1b3e74","locale":"zh-Hans","page_key":"libpq-connect.html","source_hash":"1555b03a2bc480920a9c72be9683ee3ddf99e8a5c17267c0dca73c42cd50e44c","source_revision":"unknown:rendered-translation-baseline","translated_from_revision":null,"translation_revision":"git:b1b500221dbe5437cfca004d6b04d3f6e422765d;html-sha256:08e987a66af27b98444a8057c256314eafa13611a3fb9e888214fc436824244b","url":"/zh/docs/18/libpq-connect.html#LIBPQ-CONNECT-MAX-PROTOCOL-VERSION","version":"18"},"runtime_rerun":false,"source_facts_revision":"ee8d1a3612338fd9adf250730cb640fcc5233b5491337cc00a316a44e3a0b9f8"}},"ManualEvidence":{"manual_path":"libpq-connect.html#LIBPQ-CONNECT-MAX-PROTOCOL-VERSION","release":{"channel":"stable","evidence_kind":"English 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archive","source_sha256":"555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f","source_url":"https://ftp.postgresql.org/pub/source/v18.6/postgresql-18.6.tar.bz2","svg_assets":3,"tree":"18"},"ref":"https://ftp.postgresql.org/pub/source/v18.6/postgresql-18.6.tar.bz2","revision":"ee8d1a3612338fd9adf250730cb640fcc5233b5491337cc00a316a44e3a0b9f8","source_sha256":"555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"},"sources":[{"anchor":"LIBPQ-CONNECT-MAX-PROTOCOL-VERSION","file":"libpq-connect.html","label":"18.6 English manual · libpq-connect.html","sha256":"c26a7fc3dcda6066cfe540641ae2690faf3d3c03277f30b4dfc2328ab45c212f","url":"/docs/18/libpq-connect.html#LIBPQ-CONNECT-MAX-PROTOCOL-VERSION"},{"archive_sha256":"555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f","file":"src/interfaces/libpq/fe-connect.c","label":"18.6 libpq connection option 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":"max-protocol-version","SourceDatabase":"center","Version":"18","Locale":"en","Title":"max_protocol_version","Summary":"Specifies the protocol version to request from the server. The default is to use version 3.0 of the PostgreSQL protocol, unless the connection string specifies a feature that relies on a higher protocol version, in which case the latest version supported by libpq is used. If the server does not support the protocol version requested by the client, the connection is automatically downgraded to a lower minor protocol version that the server supports. After the connection attempt has completed you can use PQfullProtocolVersion to find out which exact protocol version was negotiated.","BodyHTML":"\u003cdiv\u003e\u003cdl\u003e\u003cdt id=\"LIBPQ-CONNECT-MAX-PROTOCOL-VERSION\"\u003e\u003cspan\u003e\u003ccode\u003emax_protocol_version\u003c/code\u003e\u003c/span\u003e \u003c/dt\u003e\u003cdd\u003e\n\u003cp\u003eSpecifies the protocol version to request from the server. The default is to use version \u003ccode\u003e3.0\u003c/code\u003e of the \u003cspan\u003ePostgreSQL\u003c/span\u003e protocol, unless the connection string specifies a feature that relies on a higher protocol version, in which case the latest version supported by libpq is used. If the server does not support the protocol version requested by the client, the connection is automatically downgraded to a lower minor protocol version that the server supports. After the connection attempt has completed you can use \u003ca href=\"/docs/18/libpq-status.html#LIBPQ-PQFULLPROTOCOLVERSION\" rel=\"nofollow\"\u003e\u003ccode\u003ePQfullProtocolVersion\u003c/code\u003e\u003c/a\u003e to find out which exact protocol version was negotiated.\u003c/p\u003e\n\u003cp\u003eThe current supported values are \u003ccode\u003e3.0\u003c/code\u003e, \u003ccode\u003e3.2\u003c/code\u003e, and \u003ccode\u003elatest\u003c/code\u003e. The \u003ccode\u003elatest\u003c/code\u003e value is equivalent to the latest protocol version supported by the libpq version being used, which is currently \u003ccode\u003e3.2\u003c/code\u003e.\u003c/p\u003e\n\u003c/dd\u003e\u003c/dl\u003e\u003c/div\u003e","SourceRevision":"ee8d1a3612338fd9adf250730cb640fcc5233b5491337cc00a316a44e3a0b9f8","ContentHash":"4216ac545392974fe9f8d9716243ae2c716e58695482b14c81f80c2d3f86fc15","Payload":{"description":["Specifies the protocol version to request from the server. The default is to use version 3.0 of the PostgreSQL protocol, unless the connection string specifies a feature that relies on a higher protocol version, in which case the latest version supported by libpq is used. If the server does not support the protocol version requested by the client, the connection is automatically downgraded to a lower minor protocol version that the server supports. After the connection attempt has completed you can use PQfullProtocolVersion to find out which exact protocol version was negotiated."],"manual_html":"\u003cdiv\u003e\u003cdl class=\"variablelist\"\u003e\u003cdt id=\"LIBPQ-CONNECT-MAX-PROTOCOL-VERSION\"\u003e\u003cspan class=\"term\"\u003e\u003ccode class=\"literal\"\u003emax_protocol_version\u003c/code\u003e\u003c/span\u003e \u003c/dt\u003e\u003cdd\u003e\n\u003cp\u003eSpecifies the protocol version to request from the server. The default is to use version \u003ccode class=\"literal\"\u003e3.0\u003c/code\u003e of the \u003cspan class=\"productname\"\u003ePostgreSQL\u003c/span\u003e protocol, unless the connection string specifies a feature that relies on a higher protocol version, in which case the latest version supported by libpq is used. If the server does not support the protocol version requested by the client, the connection is automatically downgraded to a lower minor protocol version that the server supports. After the connection attempt has completed you can use \u003ca class=\"xref\" href=\"/docs/18/libpq-status.html#LIBPQ-PQFULLPROTOCOLVERSION\"\u003e\u003ccode class=\"function\"\u003ePQfullProtocolVersion\u003c/code\u003e\u003c/a\u003e to find out which exact protocol version was negotiated.\u003c/p\u003e\n\u003cp\u003eThe current supported values are \u003ccode class=\"literal\"\u003e3.0\u003c/code\u003e, \u003ccode class=\"literal\"\u003e3.2\u003c/code\u003e, and \u003ccode class=\"literal\"\u003elatest\u003c/code\u003e. The \u003ccode class=\"literal\"\u003elatest\u003c/code\u003e value is equivalent to the latest protocol version supported by the libpq version being used, which is currently \u003ccode class=\"literal\"\u003e3.2\u003c/code\u003e.\u003c/p\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":["PGMAXPROTOCOLVERSION behaves the same as the max_protocol_version connection parameter."],"title":"Environment variable evidence"}],"tables":[{"columns":[{"key":"name","label":"Variable"},{"key":"description","label":"Documented behavior"}],"key":"environment","rows":[{"description":"PGMAXPROTOCOLVERSION behaves the same as the max_protocol_version connection parameter.","name":{"text":"PGMAXPROTOCOLVERSION","url":"/docs/18/libpq-envars.html"}}],"title":"Environment fallback"}]}},"RequestedLocale":"en","Fallback":false,"Versions":["18","19","20"],"Locales":["en","zh-Hans"],"Signatures":null,"Spellings":null,"SQLState":null,"Evidence":null}