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The frontend must save these values if it wishes to be able to issue CancelRequest messages later."}, {"c0": "2", "c1": "Int32(12)", "c2": "Length of message contents in bytes, including self."}, {"c0": "3", "c1": "Int32", "c2": "The process ID of this backend."}, {"c0": "4", "c1": "Int32", "c2": "The secret key of this backend."}], "title": "Wire fields in documented order", "columns": [{"key": "c0", "label": "Position"}, {"key": "c1", "label": "Format"}, {"key": "c2", "label": "Meaning"}]}], "related": [{"url": "/docs/16/protocol-flow.html", "label": "Protocol flow and exchange examples"}, {"url": "/docs/16/protocol-overview.html", "label": "Protocol overview"}, {"url": "/docs/16/protocol-flow.html#PROTOCOL-FLOW-START-UP", "label": "Start-up"}], "release": {"ref": "https://ftp.postgresql.org/pub/source/v16.15/postgresql-16.15.tar.bz2", "label": "16.15", "major": "16", "channel": "stable", "revision": "c1575341fa7bd40f5274ea465b34390f4dc64cdd0770af327005caaeb9f6b7ed"}, "sources": [{"url": "/docs/16/protocol-message-formats.html#PROTOCOL-MESSAGE-FORMATS-BACKENDKEYDATA", "path": "protocol-message-formats.html", "label": "PostgreSQL 16 English manual", "sha256": "c15646b30727f469cdac3bd411e50dc9b14ee85982a9c9c8a2b3e16449b39a46"}], "sections": [{"title": "Framing and repetition", "paragraphs": ["The complete definition below retains repetition, counts and conditional fields. A numbered table row is a documented field definition, not a fixed byte offset. Integer encodings and flow rules follow the same-version protocol chapter."]}], "direction": "B", "signature": "BackendKeyData (B)", "description": ["BackendKeyData is a backend protocol message. Identifies the message as cancellation key data. The frontend must save these values if it wishes to be able to issue CancelRequest messages later."], "manual_html": "<dl><dd>\n<div class=\"variablelist\">\n<dl class=\"variablelist\">\n<dt><span class=\"term\">Byte1('K')</span></dt>\n<dd>\n<p>Identifies the message as cancellation key data. The frontend must save these values if it wishes to be able to issue CancelRequest messages later.</p>\n</dd>\n<dt><span class=\"term\">Int32(12)</span></dt>\n<dd>\n<p>Length of message contents in bytes, including self.</p>\n</dd>\n<dt><span class=\"term\">Int32</span></dt>\n<dd>\n<p>The process ID of this backend.</p>\n</dd>\n<dt><span class=\"term\">Int32</span></dt>\n<dd>\n<p>The secret key of this backend.</p>\n</dd>\n</dl>\n</div>\n</dd></dl>", "manual_path": "/docs/16/protocol-message-formats.html", "comparison_data": {"fields": [{"format": "Byte1('K')", "description": "Identifies the message as cancellation key data. The frontend must save these values if it wishes to be able to issue CancelRequest messages later."}, {"format": "Int32(12)", "description": "Length of message contents in bytes, including self."}, {"format": "Int32", "description": "The process ID of this backend."}, {"format": "Int32", "description": "The secret key of this backend."}], "direction": "B"}, "comparison_hash": "12c3f3028da101a4f3bbeb590a820e4fa0a6132eea3920d29f5e2a7de9c1670e"}, "17": {"facts": [{"label": "Direction", "value": "Backend \u2192 frontend"}, {"label": "First wire field", "value": "Byte1('K')"}, {"label": "Field entries", "value": "4"}, {"label": "Documented flow contexts", "value": "Start-up"}], "fields": [{"format": "Byte1('K')", "description": "Identifies the message as cancellation key data. The frontend must save these values if it wishes to be able to issue CancelRequest messages later."}, {"format": "Int32(12)", "description": "Length of message contents in bytes, including self."}, {"format": "Int32", "description": "The process ID of this backend."}, {"format": "Int32", "description": "The secret key of this backend."}], "tables": [{"key": "fields", "rows": [{"c0": "1", "c1": "Byte1('K')", "c2": "Identifies the message as cancellation key data. The frontend must save these values if it wishes to be able to issue CancelRequest messages later."}, {"c0": "2", "c1": "Int32(12)", "c2": "Length of message contents in bytes, including self."}, {"c0": "3", "c1": "Int32", "c2": "The process ID of this backend."}, {"c0": "4", "c1": "Int32", "c2": "The secret key of this backend."}], "title": "Wire fields in documented order", "columns": [{"key": "c0", "label": "Position"}, {"key": "c1", "label": "Format"}, {"key": "c2", "label": "Meaning"}]}], "related": [{"url": "/docs/17/protocol-flow.html", "label": "Protocol flow and exchange examples"}, {"url": "/docs/17/protocol-overview.html", "label": "Protocol overview"}, {"url": "/docs/17/protocol-flow.html#PROTOCOL-FLOW-START-UP", "label": "Start-up"}], "release": {"ref": "https://ftp.postgresql.org/pub/source/v17.11/postgresql-17.11.tar.bz2", "label": "17.11", "major": "17", "channel": "stable", "revision": "dd27f2b3c59e73ed14aa3324901242bf69a032a6347805f274e6260322d42979"}, "sources": [{"url": "/docs/17/protocol-message-formats.html#PROTOCOL-MESSAGE-FORMATS-BACKENDKEYDATA", "path": "protocol-message-formats.html", "label": "PostgreSQL 17 English manual", "sha256": "3c0e7b8a1a8f7ec5026226eab83d6704b7c5199ec9ba1aaaf91ea517609eed4e"}], "sections": [{"title": "Framing and repetition", "paragraphs": ["The complete definition below retains repetition, counts and conditional fields. A numbered table row is a documented field definition, not a fixed byte offset. Integer encodings and flow rules follow the same-version protocol chapter."]}], "direction": "B", "signature": "BackendKeyData (B)", "description": ["BackendKeyData is a backend protocol message. Identifies the message as cancellation key data. The frontend must save these values if it wishes to be able to issue CancelRequest messages later."], "manual_html": "<dl><dd>\n<div class=\"variablelist\">\n<dl class=\"variablelist\">\n<dt><span class=\"term\">Byte1('K')</span></dt>\n<dd>\n<p>Identifies the message as cancellation key data. The frontend must save these values if it wishes to be able to issue CancelRequest messages later.</p>\n</dd>\n<dt><span class=\"term\">Int32(12)</span></dt>\n<dd>\n<p>Length of message contents in bytes, including self.</p>\n</dd>\n<dt><span class=\"term\">Int32</span></dt>\n<dd>\n<p>The process ID of this backend.</p>\n</dd>\n<dt><span class=\"term\">Int32</span></dt>\n<dd>\n<p>The secret key of this backend.</p>\n</dd>\n</dl>\n</div>\n</dd></dl>", "manual_path": "/docs/17/protocol-message-formats.html", "comparison_data": {"fields": [{"format": "Byte1('K')", "description": "Identifies the message as cancellation key data. The frontend must save these values if it wishes to be able to issue CancelRequest messages later."}, {"format": "Int32(12)", "description": "Length of message contents in bytes, including self."}, {"format": "Int32", "description": "The process ID of this backend."}, {"format": "Int32", "description": "The secret key of this backend."}], "direction": "B"}, "comparison_hash": "12c3f3028da101a4f3bbeb590a820e4fa0a6132eea3920d29f5e2a7de9c1670e"}, "18": {"facts": [{"label": "Direction", "value": "Backend \u2192 frontend"}, {"label": "First wire field", "value": "Byte1('K')"}, {"label": "Field entries", "value": "4"}, {"label": "Documented flow contexts", "value": "Start-up"}], "fields": [{"format": "Byte1('K')", "description": "Identifies the message as cancellation key data. The frontend must save these values if it wishes to be able to issue CancelRequest messages later."}, {"format": "Int32", "description": "Length of message contents in bytes, including self."}, {"format": "Int32", "description": "The process ID of this backend."}, {"format": "Byte n", "description": "The secret key of this backend. This field extends to the end of the message, indicated by the length field. The minimum and maximum key length are 4 and 256 bytes, respectively. The PostgreSQL server only sends keys up to 32 bytes, but the larger maximum size allows for future server versions, as well as connection poolers and other middleware, to use longer keys. One possible use case is augmenting the server's key with extra information. Middleware is therefore also encouraged to not use up all of the bytes, in case multiple middleware applications are layered on top of each other, each of which may wrap the key with extra data."}], "tables": [{"key": "fields", "rows": [{"c0": "1", "c1": "Byte1('K')", "c2": "Identifies the message as cancellation key data. The frontend must save these values if it wishes to be able to issue CancelRequest messages later."}, {"c0": "2", "c1": "Int32", "c2": "Length of message contents in bytes, including self."}, {"c0": "3", "c1": "Int32", "c2": "The process ID of this backend."}, {"c0": "4", "c1": "Byte n", "c2": "The secret key of this backend. This field extends to the end of the message, indicated by the length field. The minimum and maximum key length are 4 and 256 bytes, respectively. The PostgreSQL server only sends keys up to 32 bytes, but the larger maximum size allows for future server versions, as well as connection poolers and other middleware, to use longer keys. One possible use case is augmenting the server's key with extra information. Middleware is therefore also encouraged to not use up all of the bytes, in case multiple middleware applications are layered on top of each other, each of which may wrap the key with extra data."}], "title": "Wire fields in documented order", "columns": [{"key": "c0", "label": "Position"}, {"key": "c1", "label": "Format"}, {"key": "c2", "label": "Meaning"}]}], "related": [{"url": "/docs/18/protocol-flow.html", "label": "Protocol flow and exchange examples"}, {"url": "/docs/18/protocol-overview.html", "label": "Protocol overview"}, {"url": "/docs/18/protocol-flow.html#PROTOCOL-FLOW-START-UP", "label": "Start-up"}], "release": {"ref": "https://ftp.postgresql.org/pub/source/v18.6/postgresql-18.6.tar.bz2", "label": "18.6", "major": "18", "channel": "stable", "revision": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}, "sources": [{"url": "/docs/18/protocol-message-formats.html#PROTOCOL-MESSAGE-FORMATS-BACKENDKEYDATA", "path": "protocol-message-formats.html", "label": "PostgreSQL 18 English manual", "sha256": "53f37652ac2c089e30ada87d8aee7bdd0f26695b03f275302e526a807d2a1f23"}], "sections": [{"title": "Framing and repetition", "paragraphs": ["The complete definition below retains repetition, counts and conditional fields. A numbered table row is a documented field definition, not a fixed byte offset. Integer encodings and flow rules follow the same-version protocol chapter."]}], "direction": "B", "signature": "BackendKeyData (B)", "description": ["BackendKeyData is a backend protocol message. Identifies the message as cancellation key data. The frontend must save these values if it wishes to be able to issue CancelRequest messages later."], "manual_html": "<dl><dd>\n<div class=\"variablelist\">\n<dl class=\"variablelist\">\n<dt><span class=\"term\">Byte1('K')</span></dt>\n<dd>\n<p>Identifies the message as cancellation key data. The frontend must save these values if it wishes to be able to issue CancelRequest messages later.</p>\n</dd>\n<dt><span class=\"term\">Int32</span></dt>\n<dd>\n<p>Length of message contents in bytes, including self.</p>\n</dd>\n<dt><span class=\"term\">Int32</span></dt>\n<dd>\n<p>The process ID of this backend.</p>\n</dd>\n<dt><span class=\"term\">Byte<em class=\"replaceable\"><code>n</code></em></span></dt>\n<dd>\n<p>The secret key of this backend. This field extends to the end of the message, indicated by the length field.</p>\n<p>The minimum and maximum key length are 4 and 256 bytes, respectively. The <span class=\"productname\">PostgreSQL</span> server only sends keys up to 32 bytes, but the larger maximum size allows for future server versions, as well as connection poolers and other middleware, to use longer keys. One possible use case is augmenting the server's key with extra information. Middleware is therefore also encouraged to not use up all of the bytes, in case multiple middleware applications are layered on top of each other, each of which may wrap the key with extra data.</p>\n</dd>\n</dl>\n</div>\n<p>Before protocol version 3.2, the secret key was always 4 bytes long.</p>\n</dd></dl>", "manual_path": "/docs/18/protocol-message-formats.html", "comparison_data": {"fields": [{"format": "Byte1('K')", "description": "Identifies the message as cancellation key data. The frontend must save these values if it wishes to be able to issue CancelRequest messages later."}, {"format": "Int32", "description": "Length of message contents in bytes, including self."}, {"format": "Int32", "description": "The process ID of this backend."}, {"format": "Byte n", "description": "The secret key of this backend. This field extends to the end of the message, indicated by the length field. The minimum and maximum key length are 4 and 256 bytes, respectively. The PostgreSQL server only sends keys up to 32 bytes, but the larger maximum size allows for future server versions, as well as connection poolers and other middleware, to use longer keys. One possible use case is augmenting the server's key with extra information. Middleware is therefore also encouraged to not use up all of the bytes, in case multiple middleware applications are layered on top of each other, each of which may wrap the key with extra data."}], "direction": "B"}, "comparison_hash": "849b59845ce57aff411d6d20d1a8dcfe78053ff3861c87a5d4d026cea7dfa067"}, "19": {"facts": [{"label": "Direction", "value": "Backend \u2192 frontend"}, {"label": "First wire field", "value": "Byte1('K')"}, {"label": "Field entries", "value": "4"}, {"label": "Documented flow contexts", "value": "Start-up"}], "fields": [{"format": "Byte1('K')", "description": "Identifies the message as cancellation key data. The frontend must save these values if it wishes to be able to issue CancelRequest messages later."}, {"format": "Int32", "description": "Length of message contents in bytes, including self."}, {"format": "Int32", "description": "The process ID of this backend."}, {"format": "Byte n", "description": "The secret key of this backend. This field extends to the end of the message, indicated by the length field. The minimum and maximum key length are 4 and 256 bytes, respectively. The PostgreSQL server only sends keys up to 32 bytes, but the larger maximum size allows for future server versions, as well as connection poolers and other middleware, to use longer keys. One possible use case is augmenting the server's key with extra information. Middleware is therefore also encouraged to not use up all of the bytes, in case multiple middleware applications are layered on top of each other, each of which may wrap the key with extra data."}], "tables": [{"key": "fields", "rows": [{"c0": "1", "c1": "Byte1('K')", "c2": "Identifies the message as cancellation key data. The frontend must save these values if it wishes to be able to issue CancelRequest messages later."}, {"c0": "2", "c1": "Int32", "c2": "Length of message contents in bytes, including self."}, {"c0": "3", "c1": "Int32", "c2": "The process ID of this backend."}, {"c0": "4", "c1": "Byte n", "c2": "The secret key of this backend. This field extends to the end of the message, indicated by the length field. The minimum and maximum key length are 4 and 256 bytes, respectively. The PostgreSQL server only sends keys up to 32 bytes, but the larger maximum size allows for future server versions, as well as connection poolers and other middleware, to use longer keys. One possible use case is augmenting the server's key with extra information. Middleware is therefore also encouraged to not use up all of the bytes, in case multiple middleware applications are layered on top of each other, each of which may wrap the key with extra data."}], "title": "Wire fields in documented order", "columns": [{"key": "c0", "label": "Position"}, {"key": "c1", "label": "Format"}, {"key": "c2", "label": "Meaning"}]}], "related": [{"url": "/docs/19/protocol-flow.html", "label": "Protocol flow and exchange examples"}, {"url": "/docs/19/protocol-overview.html", "label": "Protocol overview"}, {"url": "/docs/19/protocol-flow.html#PROTOCOL-FLOW-START-UP", "label": "Start-up"}], "release": {"ref": "https://ftp.postgresql.org/pub/source/v19beta4/postgresql-19beta4.tar.bz2", "label": "19beta4", "major": "19", "channel": "preview", "revision": "83157ee9c599d03b2f7a3d73ef3a56ec24e0e79cc2b3501a64d1364f56398c86"}, "sources": [{"url": "/docs/19/protocol-message-formats.html#PROTOCOL-MESSAGE-FORMATS-BACKENDKEYDATA", "path": "protocol-message-formats.html", "label": "PostgreSQL 19 English manual", "sha256": "90ffd4417d4975d088424b23a513f1d79ac914225ad7e239a12f44d0dd2248e4"}], "sections": [{"title": "Framing and repetition", "paragraphs": ["The complete definition below retains repetition, counts and conditional fields. A numbered table row is a documented field definition, not a fixed byte offset. Integer encodings and flow rules follow the same-version protocol chapter."]}], "direction": "B", "signature": "BackendKeyData (B)", "description": ["BackendKeyData is a backend protocol message. Identifies the message as cancellation key data. The frontend must save these values if it wishes to be able to issue CancelRequest messages later."], "manual_html": "<dl><dd>\n<div class=\"variablelist\">\n<dl class=\"variablelist\">\n<dt><span class=\"term\">Byte1('K')</span></dt>\n<dd>\n<p>Identifies the message as cancellation key data. The frontend must save these values if it wishes to be able to issue CancelRequest messages later.</p>\n</dd>\n<dt><span class=\"term\">Int32</span></dt>\n<dd>\n<p>Length of message contents in bytes, including self.</p>\n</dd>\n<dt><span class=\"term\">Int32</span></dt>\n<dd>\n<p>The process ID of this backend.</p>\n</dd>\n<dt><span class=\"term\">Byte<em class=\"replaceable\"><code>n</code></em></span></dt>\n<dd>\n<p>The secret key of this backend. This field extends to the end of the message, indicated by the length field.</p>\n<p>The minimum and maximum key length are 4 and 256 bytes, respectively. The <span class=\"productname\">PostgreSQL</span> server only sends keys up to 32 bytes, but the larger maximum size allows for future server versions, as well as connection poolers and other middleware, to use longer keys. One possible use case is augmenting the server's key with extra information. Middleware is therefore also encouraged to not use up all of the bytes, in case multiple middleware applications are layered on top of each other, each of which may wrap the key with extra data.</p>\n</dd>\n</dl>\n</div>\n<p>Before protocol version 3.2, the secret key was always 4 bytes long.</p>\n</dd></dl>", "manual_path": "/docs/19/protocol-message-formats.html", "comparison_data": {"fields": [{"format": "Byte1('K')", "description": "Identifies the message as cancellation key data. The frontend must save these values if it wishes to be able to issue CancelRequest messages later."}, {"format": "Int32", "description": "Length of message contents in bytes, including self."}, {"format": "Int32", "description": "The process ID of this backend."}, {"format": "Byte n", "description": "The secret key of this backend. This field extends to the end of the message, indicated by the length field. The minimum and maximum key length are 4 and 256 bytes, respectively. 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The frontend must save these values if it wishes to be able to issue CancelRequest messages later."}, {"format": "Int32", "description": "Length of message contents in bytes, including self."}, {"format": "Int32", "description": "The process ID of this backend."}, {"format": "Byte n", "description": "The secret key of this backend. This field extends to the end of the message, indicated by the length field. The minimum and maximum key length are 4 and 256 bytes, respectively. The PostgreSQL server only sends keys up to 32 bytes, but the larger maximum size allows for future server versions, as well as connection poolers and other middleware, to use longer keys. One possible use case is augmenting the server's key with extra information. Middleware is therefore also encouraged to not use up all of the bytes, in case multiple middleware applications are layered on top of each other, each of which may wrap the key with extra data."}], "tables": [{"key": "fields", "rows": [{"c0": "1", "c1": "Byte1('K')", "c2": "Identifies the message as cancellation key data. The frontend must save these values if it wishes to be able to issue CancelRequest messages later."}, {"c0": "2", "c1": "Int32", "c2": "Length of message contents in bytes, including self."}, {"c0": "3", "c1": "Int32", "c2": "The process ID of this backend."}, {"c0": "4", "c1": "Byte n", "c2": "The secret key of this backend. This field extends to the end of the message, indicated by the length field. The minimum and maximum key length are 4 and 256 bytes, respectively. The PostgreSQL server only sends keys up to 32 bytes, but the larger maximum size allows for future server versions, as well as connection poolers and other middleware, to use longer keys. One possible use case is augmenting the server's key with extra information. 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Middleware is therefore also encouraged to not use up all of the bytes, in case multiple middleware applications are layered on top of each other, each of which may wrap the key with extra data.</p>\n</dd>\n</dl>\n</div>\n<p>Before protocol version 3.2, the secret key was always 4 bytes long.</p>\n</dd></dl>", "manual_path": "/docs/devel/protocol-message-formats.html", "comparison_data": {"fields": [{"format": "Byte1('K')", "description": "Identifies the message as cancellation key data. The frontend must save these values if it wishes to be able to issue CancelRequest messages later."}, {"format": "Int32", "description": "Length of message contents in bytes, including self."}, {"format": "Int32", "description": "The process ID of this backend."}, {"format": "Byte n", "description": "The secret key of this backend. This field extends to the end of the message, indicated by the length field. The minimum and maximum key length are 4 and 256 bytes, respectively. The PostgreSQL server only sends keys up to 32 bytes, but the larger maximum size allows for future server versions, as well as connection poolers and other middleware, to use longer keys. One possible use case is augmenting the server's key with extra information. Middleware is therefore also encouraged to not use up all of the bytes, in case multiple middleware applications are layered on top of each other, each of which may wrap the key with extra data."}], "direction": "B"}, "comparison_hash": "849b59845ce57aff411d6d20d1a8dcfe78053ff3861c87a5d4d026cea7dfa067"}}}, "snapshot": {"facts": [{"label": "Direction", "value": "Backend \u2192 frontend"}, {"label": "First wire field", "value": "Byte1('K')"}, {"label": "Field entries", "value": "4"}, {"label": "Documented flow contexts", "value": "Start-up"}], "fields": [{"format": "Byte1('K')", "description": "Identifies the message as cancellation key data. The frontend must save these values if it wishes to be able to issue CancelRequest messages later."}, {"format": "Int32", "description": "Length of message contents in bytes, including self."}, {"format": "Int32", "description": "The process ID of this backend."}, {"format": "Byte n", "description": "The secret key of this backend. This field extends to the end of the message, indicated by the length field. The minimum and maximum key length are 4 and 256 bytes, respectively. The PostgreSQL server only sends keys up to 32 bytes, but the larger maximum size allows for future server versions, as well as connection poolers and other middleware, to use longer keys. One possible use case is augmenting the server's key with extra information. Middleware is therefore also encouraged to not use up all of the bytes, in case multiple middleware applications are layered on top of each other, each of which may wrap the key with extra data."}], "tables": [{"key": "fields", "rows": [{"c0": "1", "c1": "Byte1('K')", "c2": "Identifies the message as cancellation key data. The frontend must save these values if it wishes to be able to issue CancelRequest messages later."}, {"c0": "2", "c1": "Int32", "c2": "Length of message contents in bytes, including self."}, {"c0": "3", "c1": "Int32", "c2": "The process ID of this backend."}, {"c0": "4", "c1": "Byte n", "c2": "The secret key of this backend. This field extends to the end of the message, indicated by the length field. The minimum and maximum key length are 4 and 256 bytes, respectively. The PostgreSQL server only sends keys up to 32 bytes, but the larger maximum size allows for future server versions, as well as connection poolers and other middleware, to use longer keys. One possible use case is augmenting the server's key with extra information. Middleware is therefore also encouraged to not use up all of the bytes, in case multiple middleware applications are layered on top of each other, each of which may wrap the key with extra data."}], "title": "Wire fields in documented order", "columns": [{"key": "c0", "label": "Position"}, {"key": "c1", "label": "Format"}, {"key": "c2", "label": "Meaning"}]}], "related": [{"url": "/docs/18/protocol-flow.html", "label": "Protocol flow and exchange examples"}, {"url": "/docs/18/protocol-overview.html", "label": "Protocol overview"}, {"url": "/docs/18/protocol-flow.html#PROTOCOL-FLOW-START-UP", "label": "Start-up"}], "release": {"ref": "https://ftp.postgresql.org/pub/source/v18.6/postgresql-18.6.tar.bz2", "label": "18.6", "major": "18", "channel": "stable", "revision": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}, "sources": [{"url": "/docs/18/protocol-message-formats.html#PROTOCOL-MESSAGE-FORMATS-BACKENDKEYDATA", "path": "protocol-message-formats.html", "label": "PostgreSQL 18 English manual", "sha256": "53f37652ac2c089e30ada87d8aee7bdd0f26695b03f275302e526a807d2a1f23"}], "sections": [{"title": "Framing and repetition", "paragraphs": ["The complete definition below retains repetition, counts and conditional fields. A numbered table row is a documented field definition, not a fixed byte offset. Integer encodings and flow rules follow the same-version protocol chapter."]}], "direction": "B", "signature": "BackendKeyData (B)", "description": ["BackendKeyData is a backend protocol message. Identifies the message as cancellation key data. The frontend must save these values if it wishes to be able to issue CancelRequest messages later."], "manual_html": "<dl><dd>\n<div class=\"variablelist\">\n<dl class=\"variablelist\">\n<dt><span class=\"term\">Byte1('K')</span></dt>\n<dd>\n<p>Identifies the message as cancellation key data. The frontend must save these values if it wishes to be able to issue CancelRequest messages later.</p>\n</dd>\n<dt><span class=\"term\">Int32</span></dt>\n<dd>\n<p>Length of message contents in bytes, including self.</p>\n</dd>\n<dt><span class=\"term\">Int32</span></dt>\n<dd>\n<p>The process ID of this backend.</p>\n</dd>\n<dt><span class=\"term\">Byte<em class=\"replaceable\"><code>n</code></em></span></dt>\n<dd>\n<p>The secret key of this backend. This field extends to the end of the message, indicated by the length field.</p>\n<p>The minimum and maximum key length are 4 and 256 bytes, respectively. The <span class=\"productname\">PostgreSQL</span> server only sends keys up to 32 bytes, but the larger maximum size allows for future server versions, as well as connection poolers and other middleware, to use longer keys. One possible use case is augmenting the server's key with extra information. Middleware is therefore also encouraged to not use up all of the bytes, in case multiple middleware applications are layered on top of each other, each of which may wrap the key with extra data.</p>\n</dd>\n</dl>\n</div>\n<p>Before protocol version 3.2, the secret key was always 4 bytes long.</p>\n</dd></dl>", "manual_path": "/docs/18/protocol-message-formats.html", "comparison_data": {"fields": [{"format": "Byte1('K')", "description": "Identifies the message as cancellation key data. The frontend must save these values if it wishes to be able to issue CancelRequest messages later."}, {"format": "Int32", "description": "Length of message contents in bytes, including self."}, {"format": "Int32", "description": "The process ID of this backend."}, {"format": "Byte n", "description": "The secret key of this backend. This field extends to the end of the message, indicated by the length field. The minimum and maximum key length are 4 and 256 bytes, respectively. The PostgreSQL server only sends keys up to 32 bytes, but the larger maximum size allows for future server versions, as well as connection poolers and other middleware, to use longer keys. One possible use case is augmenting the server's key with extra information. Middleware is therefore also encouraged to not use up all of the bytes, in case multiple middleware applications are layered on top of each other, each of which may wrap the key with extra data."}], "direction": "B"}, "comparison_hash": "849b59845ce57aff411d6d20d1a8dcfe78053ff3861c87a5d4d026cea7dfa067"}, "comparison": {"left": "17", "right": "18", "status": "changed", "diff": "--- PostgreSQL 17\n+++ PostgreSQL 18\n@@ -7,15 +7,15 @@\n     },\n     {\n       \"description\": \"Length of message contents in bytes, including self.\",\n-      \"format\": \"Int32(12)\"\n+      \"format\": \"Int32\"\n     },\n     {\n       \"description\": \"The process ID of this backend.\",\n       \"format\": \"Int32\"\n     },\n     {\n-      \"description\": \"The secret key of this backend.\",\n-      \"format\": \"Int32\"\n+      \"description\": \"The secret key of this backend. This field extends to the end of the message, indicated by the length field. The minimum and maximum key length are 4 and 256 bytes, respectively. The PostgreSQL server only sends keys up to 32 bytes, but the larger maximum size allows for future server versions, as well as connection poolers and other middleware, to use longer keys. One possible use case is augmenting the server's key with extra information. Middleware is therefore also encouraged to not use up all of the bytes, in case multiple middleware applications are layered on top of each other, each of which may wrap the key with extra data.\",\n+      \"format\": \"Byte n\"\n     }\n   ]\n }"}}