FOR KEY SHARE

commands

map[label:SELECT FOR KEY SHARE note:Lock selected rows, with ROW SHARE on the target table. NOWAIT and SKIP LOCKED affect waiting, not mode compatibility. slug:select source:map[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:0ecc8fb9e712], map[label:INSERT (foreign-key check) note:Checking a non-null foreign key locks matching rows in the referenced table FOR KEY SHARE. The check can run immediately or be deferred. Cascading actions require their own UPDATE or DELETE locks. slug:insert source:map[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] source_url:https://github.com/postgres/postgres/blob/753057e340da8f22e57c9a409ea7a235fd6a46bd/src/backend/utils/adt/ri_triggers.c variant:ffddc0fc16b6], map[label:UPDATE (foreign-key check) note:Checking a non-null foreign key locks matching rows in the referenced table FOR KEY SHARE. The check can run immediately or be deferred. Cascading actions require their own UPDATE or DELETE locks. slug:update source:map[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] source_url:https://github.com/postgres/postgres/blob/753057e340da8f22e57c9a409ea7a235fd6a46bd/src/backend/utils/adt/ri_triggers.c variant:65d8638ef74c], map[label:COPY … FROM (foreign-key check) note:Checking a non-null foreign key locks matching rows in the referenced table FOR KEY SHARE. The check can run immediately or be deferred. Cascading actions require their own UPDATE or DELETE locks. slug:copy source:map[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] source_url:https://github.com/postgres/postgres/blob/753057e340da8f22e57c9a409ea7a235fd6a46bd/src/backend/utils/adt/ri_triggers.c variant:b85f269c1b8e], map[label:MERGE (foreign-key check) note:Checking a non-null foreign key locks matching rows in the referenced table FOR KEY SHARE. The check can run immediately or be deferred. Cascading actions require their own UPDATE or DELETE locks. slug:merge source:map[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] source_url:https://github.com/postgres/postgres/blob/753057e340da8f22e57c9a409ea7a235fd6a46bd/src/backend/utils/adt/ri_triggers.c variant:e00dfdc184d6]

provenance

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summary

Behaves similarly to FOR SHARE, except that the lock is weaker: SELECT FOR UPDATE is blocked, but not SELECT FOR NO KEY UPDATE. A key-shared lock blocks other transactions from performing DELETE or any UPDATE that changes the key values, but not other UPDATE, and neither does it prevent SELECT FOR NO KEY UPDATE, SELECT FOR SHARE, or SELECT FOR KEY SHARE.