{"Entry":{"collection":"lock","key":"for-update","name":"FOR UPDATE","aliases":[],"metadata":{"abbrev":"FU","content_hash":"a9f3719df1eb261b45b07e2ed5d7b7922ee7ed28f62ca0ac8ed127b0d496ea63","imported_at":"2026-09-27T17:58:01.278734+08:00","name":"FOR UPDATE","name_zh":"FOR UPDATE","position":11,"scope":"row","slug":"for-update","source_rev":"10:f4e8f137bfb08a664c8288824c1e36b5143ac875;11:170e416034ec0231d9e9238f2577eeb76ca8d181;12:3f302f0ed06f69c5ebd33d4df95895323a3cbef6;13:05f6c9ec2c475fae8fdd56ae40bd01afcf70d1f2;14:fba35c7c28a567839faba867db0808564c0a66db;15:0351991b8e7c7b64382e2f30ce581a8f276590a6;16:dcc37b7099a9f3cf2c75167d8dc92e75f96bc1fa;17:163288afd32a448244c8df75b3c33181aadd7f20;18:753057e340da8f22e57c9a409ea7a235fd6a46bd;19:b73d13c32c834a2c8e1c60cb92f79530376cedf1;20:2c10c2ce4d7bcd57543a49ab402af02a39724e0a","summary":"FOR UPDATE causes the rows retrieved by the SELECT statement to be locked as though for update. This prevents them from being locked, modified or deleted by other transactions until the current transaction ends. That is, other transactions that attempt UPDATE, DELETE, SELECT FOR UPDATE, SELECT FOR NO KEY UPDATE, SELECT FOR SHARE or SELECT FOR KEY SHARE of these rows will be blocked until the current transaction ends; conversely, SELECT FOR UPDATE will wait for a concurrent transaction that has run any of those commands on the same row, and will then lock and return the updated row (or no row, if the row was deleted). Within a REPEATABLE READ or SERIALIZABLE transaction, however, an error will be thrown if a row to be locked has changed since the transaction started. For further discussion see Data Consistency Checks at the Application Level."}},"Definition":{"Collection":"lock","Key":"for-update","SourceDatabase":"center","Version":"18","SourceTable":"lock_mode","SourceKey":"for-update","SourceRevision":"10:f4e8f137bfb08a664c8288824c1e36b5143ac875;11:170e416034ec0231d9e9238f2577eeb76ca8d181;12:3f302f0ed06f69c5ebd33d4df95895323a3cbef6;13:05f6c9ec2c475fae8fdd56ae40bd01afcf70d1f2;14:fba35c7c28a567839faba867db0808564c0a66db;15:0351991b8e7c7b64382e2f30ce581a8f276590a6;16:dcc37b7099a9f3cf2c75167d8dc92e75f96bc1fa;17:163288afd32a448244c8df75b3c33181aadd7f20;18:753057e340da8f22e57c9a409ea7a235fd6a46bd;19:b73d13c32c834a2c8e1c60cb92f79530376cedf1;20:2c10c2ce4d7bcd57543a49ab402af02a39724e0a","Facts":{"commands":[{"label":"SELECT FOR UPDATE","note":"Lock selected rows, with ROW SHARE on the target table. 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An insert-only action does not use this row lock.","slug":"merge","source":{"kind":"documentation","path":"doc/src/sgml/mvcc.sgml","revision":"753057e340da8f22e57c9a409ea7a235fd6a46bd","sha256":"4b7bf77ee0af4b86052330ff2421d567df3604b75fe7d4f522bec84fdea87340","url":"https://raw.githubusercontent.com/postgres/postgres/753057e340da8f22e57c9a409ea7a235fd6a46bd/doc/src/sgml/mvcc.sgml"},"source_url":"https://www.postgresql.org/docs/18/explicit-locking.html","variant":"8341438966ce"},{"label":"INSERT … ON CONFLICT DO UPDATE (key)","note":"The conflict action updates key columns of an existing row. This is not a fixed row lock for every INSERT.","slug":"insert","source":{"kind":"command-documentation","path":"doc/src/sgml/ref/insert.sgml","revision":"753057e340da8f22e57c9a409ea7a235fd6a46bd","sha256":"f93403779fb1d980cd5995a1e2741bbdae8404584407610f9aba33ec4724a39f","url":"https://raw.githubusercontent.com/postgres/postgres/753057e340da8f22e57c9a409ea7a235fd6a46bd/doc/src/sgml/ref/insert.sgml"},"source_url":"https://www.postgresql.org/docs/18/sql-insert.html","variant":"211a0191f91b"}],"conflicts":["for-key-share","for-share","for-no-key-update","for-update"],"description":["FOR UPDATE causes the rows retrieved by the SELECT statement to be locked as though for update. This prevents them from being locked, modified or deleted by other transactions until the current transaction ends. That is, other transactions that attempt UPDATE, DELETE, SELECT FOR UPDATE, SELECT FOR NO KEY UPDATE, SELECT FOR SHARE or SELECT FOR KEY SHARE of these rows will be blocked until the current transaction ends; conversely, SELECT FOR UPDATE will wait for a concurrent transaction that has run any of those commands on the same row, and will then lock and return the updated row (or no row, if the row was deleted). Within a REPEATABLE READ or SERIALIZABLE transaction, however, an error will be thrown if a row to be locked has changed since the transaction started. For further discussion see Data Consistency Checks at the Application Level.","The FOR UPDATE lock mode is also acquired by any DELETE on a row, and also by an UPDATE that modifies the values of certain columns. Currently, the set of columns considered for the UPDATE case are those that have a unique index on them that can be used in a foreign key (so partial indexes and expressional indexes are not considered), but this may change in the future."],"provenance":{"doc_slug":"18","fetched_at":"2026-09-27T09:39:42+00:00","label":"18","major":"18","official_url":"https://www.postgresql.org/docs/18/explicit-locking.html","ref":"REL_18_STABLE","revision":"753057e340da8f22e57c9a409ea7a235fd6a46bd","sources":[{"kind":"command-documentation","path":"doc/src/sgml/ref/alter_index.sgml","revision":"753057e340da8f22e57c9a409ea7a235fd6a46bd","sha256":"746cd43287186dfbfa6acf77fd5c6713e66919653fb00af5476a0baa65988e7a","url":"https://raw.githubusercontent.com/postgres/postgres/753057e340da8f22e57c9a409ea7a235fd6a46bd/doc/src/sgml/ref/alter_index.sgml"},{"kind":"command-documentation","path":"doc/src/sgml/ref/alter_table.sgml","revision":"753057e340da8f22e57c9a409ea7a235fd6a46bd","sha256":"10436673fa2f093bdf51986a06d22dd748a9bb003bcd5517db2a65fba569a3c9","url":"https://raw.githubusercontent.com/postgres/postgres/753057e340da8f22e57c9a409ea7a235fd6a46bd/doc/src/sgml/ref/alter_table.sgml"},{"kind":"command-documentation","path":"doc/src/sgml/ref/comment.sgml","revision":"753057e340da8f22e57c9a409ea7a235fd6a46bd","sha256":"d0048329d237192696d7ccb9471aba4137d943556fdb770e2ffb3cf6c511c18f","url":"https://raw.githubusercontent.com/postgres/postgres/753057e340da8f22e57c9a409ea7a235fd6a46bd/doc/src/sgml/ref/comment.sgml"},{"kind":"source","path":"src/backend/commands/copy.c","revision":"753057e340da8f22e57c9a409ea7a235fd6a46bd","sha256":"f50ecc1531109fc172d841d461e209cef611f3d017ef4184034c39e128deabbe","url":"https://raw.githubusercontent.com/postgres/postgres/753057e340da8f22e57c9a409ea7a235fd6a46bd/src/backend/commands/copy.c"},{"kind":"command-documentation","path":"doc/src/sgml/ref/create_index.sgml","revision":"753057e340da8f22e57c9a409ea7a235fd6a46bd","sha256":"3698f11c6f447d127e4624a1a845dee4d5146b8337ddc6d895a7962e676717f8","url":"https://raw.githubusercontent.com/postgres/postgres/753057e340da8f22e57c9a409ea7a235fd6a46bd/doc/src/sgml/ref/create_index.sgml"},{"kind":"source","path":"src/backend/access/heap/heapam.c","revision":"753057e340da8f22e57c9a409ea7a235fd6a46bd","sha256":"bca2ca0746a1862016bdb416b8482441a7b16360f71afe5e4abf6dbae0fa0c72","url":"https://raw.githubusercontent.com/postgres/postgres/753057e340da8f22e57c9a409ea7a235fd6a46bd/src/backend/access/heap/heapam.c"},{"kind":"source","path":"src/backend/catalog/index.c","revision":"753057e340da8f22e57c9a409ea7a235fd6a46bd","sha256":"98a4156a5c21ae856a3b583b633cdeb578a5b69910386c9f166d69fcb04ba2d0","url":"https://raw.githubusercontent.com/postgres/postgres/753057e340da8f22e57c9a409ea7a235fd6a46bd/src/backend/catalog/index.c"},{"kind":"command-documentation","path":"doc/src/sgml/ref/insert.sgml","revision":"753057e340da8f22e57c9a409ea7a235fd6a46bd","sha256":"f93403779fb1d980cd5995a1e2741bbdae8404584407610f9aba33ec4724a39f","url":"https://raw.githubusercontent.com/postgres/postgres/753057e340da8f22e57c9a409ea7a235fd6a46bd/doc/src/sgml/ref/insert.sgml"},{"kind":"source","path":"src/backend/storage/lmgr/lock.c","revision":"753057e340da8f22e57c9a409ea7a235fd6a46bd","sha256":"e7f43560bf6a8417ff46991238084b6edeb44a995b87670ed1f7fa6f1515276b","url":"https://raw.githubusercontent.com/postgres/postgres/753057e340da8f22e57c9a409ea7a235fd6a46bd/src/backend/storage/lmgr/lock.c"},{"kind":"documentation","path":"doc/src/sgml/mvcc.sgml","revision":"753057e340da8f22e57c9a409ea7a235fd6a46bd","sha256":"4b7bf77ee0af4b86052330ff2421d567df3604b75fe7d4f522bec84fdea87340","url":"https://raw.githubusercontent.com/postgres/postgres/753057e340da8f22e57c9a409ea7a235fd6a46bd/doc/src/sgml/mvcc.sgml"},{"kind":"command-documentation","path":"doc/src/sgml/ref/reindex.sgml","revision":"753057e340da8f22e57c9a409ea7a235fd6a46bd","sha256":"5e889d6e1d9b09d5f9cd3f7086ca13f540da0fe8262cdd8a9037ce9aa6f1dfdf","url":"https://raw.githubusercontent.com/postgres/postgres/753057e340da8f22e57c9a409ea7a235fd6a46bd/doc/src/sgml/ref/reindex.sgml"},{"kind":"source","path":"src/backend/utils/adt/ri_triggers.c","revision":"753057e340da8f22e57c9a409ea7a235fd6a46bd","sha256":"a3fed49fbda88fe0fe5bcf35eb019fced28596ae4046233f2acb2eb9f90ab1da","url":"https://raw.githubusercontent.com/postgres/postgres/753057e340da8f22e57c9a409ea7a235fd6a46bd/src/backend/utils/adt/ri_triggers.c"},{"kind":"source","path":"src/backend/commands/tablecmds.c","revision":"753057e340da8f22e57c9a409ea7a235fd6a46bd","sha256":"df8817816f893e73d5648fea169e222ba33320e5b24bf755b424b29098f4e7da","url":"https://raw.githubusercontent.com/postgres/postgres/753057e340da8f22e57c9a409ea7a235fd6a46bd/src/backend/commands/tablecmds.c"},{"kind":"command-documentation","path":"doc/src/sgml/ref/vacuum.sgml","revision":"753057e340da8f22e57c9a409ea7a235fd6a46bd","sha256":"80ca5592cda7b74938385f84f09faac33574374c1a05d605a2d55982e4cf1bbf","url":"https://raw.githubusercontent.com/postgres/postgres/753057e340da8f22e57c9a409ea7a235fd6a46bd/doc/src/sgml/ref/vacuum.sgml"},{"kind":"source","path":"src/backend/access/heap/vacuumlazy.c","revision":"753057e340da8f22e57c9a409ea7a235fd6a46bd","sha256":"90932e3b1a7b5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This prevents them from being locked, modified or deleted by other transactions until the current transaction ends. That is, other transactions that attempt UPDATE, DELETE, SELECT FOR UPDATE, SELECT FOR NO KEY UPDATE, SELECT FOR SHARE or SELECT FOR KEY SHARE of these rows will be blocked until the current transaction ends; conversely, SELECT FOR UPDATE will wait for a concurrent transaction that has run any of those commands on the same row, and will then lock and return the updated row (or no row, if the row was deleted). Within a REPEATABLE READ or SERIALIZABLE transaction, however, an error will be thrown if a row to be locked has changed since the transaction started. For further discussion see Data Consistency Checks at the Application Level."},"ManualEvidence":{"sources":[{"kind":"documentation","path":"doc/src/sgml/mvcc.sgml","revision":"753057e340da8f22e57c9a409ea7a235fd6a46bd","sha256":"4b7bf77ee0af4b86052330ff2421d567df3604b75fe7d4f522bec84fdea87340","url":"https://raw.githubusercontent.com/postgres/postgres/753057e340da8f22e57c9a409ea7a235fd6a46bd/doc/src/sgml/mvcc.sgml"},{"kind":"source","path":"src/backend/storage/lmgr/lock.c","revision":"753057e340da8f22e57c9a409ea7a235fd6a46bd","sha256":"e7f43560bf6a8417ff46991238084b6edeb44a995b87670ed1f7fa6f1515276b","url":"https://raw.githubusercontent.com/postgres/postgres/753057e340da8f22e57c9a409ea7a235fd6a46bd/src/backend/storage/lmgr/lock.c"},{"kind":"source","path":"src/backend/access/heap/heapam.c","revision":"753057e340da8f22e57c9a409ea7a235fd6a46bd","sha256":"bca2ca0746a1862016bdb416b8482441a7b16360f71afe5e4abf6dbae0fa0c72","url":"https://raw.githubusercontent.com/postgres/postgres/753057e340da8f22e57c9a409ea7a235fd6a46bd/src/backend/access/heap/heapam.c"}]},"MeasuredEvidence":{}},"Text":{"Collection":"lock","Key":"for-update","SourceDatabase":"center","Version":"18","Locale":"en","Title":"FOR UPDATE","Summary":"FOR UPDATE causes the rows retrieved by the SELECT statement to be locked as though for update. This prevents them from being locked, modified or deleted by other transactions until the current transaction ends. That is, other transactions that attempt UPDATE, DELETE, SELECT FOR UPDATE, SELECT FOR NO KEY UPDATE, SELECT FOR SHARE or SELECT FOR KEY SHARE of these rows will be blocked until the current transaction ends; conversely, SELECT FOR UPDATE will wait for a concurrent transaction that has run any of those commands on the same row, and will then lock and return the updated row (or no row, if the row was deleted). Within a REPEATABLE READ or SERIALIZABLE transaction, however, an error will be thrown if a row to be locked has changed since the transaction started. For further discussion see Data Consistency Checks at the Application Level.\nThe FOR UPDATE lock mode is also acquired by any DELETE on a row, and also by an UPDATE that modifies the values of certain columns. Currently, the set of columns considered for the UPDATE case are those that have a unique index on them that can be used in a foreign key (so partial indexes and expressional indexes are not considered), but this may change in the future.","BodyHTML":"\u003cp\u003eFOR UPDATE causes the rows retrieved by the SELECT statement to be locked as though for update. This prevents them from being locked, modified or deleted by other transactions until the current transaction ends. That is, other transactions that attempt UPDATE, DELETE, SELECT FOR UPDATE, SELECT FOR NO KEY UPDATE, SELECT FOR SHARE or SELECT FOR KEY SHARE of these rows will be blocked until the current transaction ends; conversely, SELECT FOR UPDATE will wait for a concurrent transaction that has run any of those commands on the same row, and will then lock and return the updated row (or no row, if the row was deleted). Within a REPEATABLE READ or SERIALIZABLE transaction, however, an error will be thrown if a row to be locked has changed since the transaction started. For further discussion see Data Consistency Checks at the Application Level.\nThe FOR UPDATE lock mode is also acquired by any DELETE on a row, and also by an UPDATE that modifies the values of certain columns. Currently, the set of columns considered for the UPDATE case are those that have a unique index on them that can be used in a foreign key (so partial indexes and expressional indexes are not considered), but this may change in the future.\u003c/p\u003e","SourceRevision":"10:f4e8f137bfb08a664c8288824c1e36b5143ac875;11:170e416034ec0231d9e9238f2577eeb76ca8d181;12:3f302f0ed06f69c5ebd33d4df95895323a3cbef6;13:05f6c9ec2c475fae8fdd56ae40bd01afcf70d1f2;14:fba35c7c28a567839faba867db0808564c0a66db;15:0351991b8e7c7b64382e2f30ce581a8f276590a6;16:dcc37b7099a9f3cf2c75167d8dc92e75f96bc1fa;17:163288afd32a448244c8df75b3c33181aadd7f20;18:753057e340da8f22e57c9a409ea7a235fd6a46bd;19:b73d13c32c834a2c8e1c60cb92f79530376cedf1;20:2c10c2ce4d7bcd57543a49ab402af02a39724e0a","ContentHash":"90d624e0f8fbf29444a15f31233bfe13927976c209766da461afda15e892c10f","Payload":{"description":["FOR UPDATE causes the rows retrieved by the SELECT statement to be locked as though for update. This prevents them from being locked, modified or deleted by other transactions until the current transaction ends. That is, other transactions that attempt UPDATE, DELETE, SELECT FOR UPDATE, SELECT FOR NO KEY UPDATE, SELECT FOR SHARE or SELECT FOR KEY SHARE of these rows will be blocked until the current transaction ends; conversely, SELECT FOR UPDATE will wait for a concurrent transaction that has run any of those commands on the same row, and will then lock and return the updated row (or no row, if the row was deleted). Within a REPEATABLE READ or SERIALIZABLE transaction, however, an error will be thrown if a row to be locked has changed since the transaction started. For further discussion see Data Consistency Checks at the Application Level.","The FOR UPDATE lock mode is also acquired by any DELETE on a row, and also by an UPDATE that modifies the values of certain columns. Currently, the set of columns considered for the UPDATE case are those that have a unique index on them that can be used in a foreign key (so partial indexes and expressional indexes are not considered), but this may change in the future."]}},"RequestedLocale":"zh-Hans","Fallback":true,"Versions":["10","11","12","13","14","15","16","17","18","19","20"],"Locales":["en"],"Signatures":null,"Spellings":null,"SQLState":null,"Evidence":null}