{"Entry":{"collection":"guc","key":"transaction_read_only","name":"transaction_read_only","aliases":[],"metadata":{"baseline":false,"boot_human":"Not specified","boot_val":null,"category":"Client Connection Defaults / Statement Behavior","category_zh":"","changed_in":[],"changes":[{"documentation_changed":false,"fields":{},"from":"8.4","status":"added","to":"9.0"},{"documentation_changed":true,"fields":{},"from":"9.5","status":"changed","to":"9.6"}],"content_hash":"533b3e60abd302cdb811d063c5934dd81cfd0d94119798af48baf3bf998cc4e8","context":"","default_changed_in":[],"default_history":[{"from":"9.0","to":"19","value":"off"}],"derived_content_hash":"1c297e39d742d825be12374688ccff30fadde5efb77acb5ff965e7ef683df2ff","editorial":{"advice":{"olap":"For reporting, consider a read-only transaction and an isolation choice that matches snapshot requirements; use deferrability only with read-only serializable work.","oltp":"Choose transaction_read_only for correctness semantics first. Keep the common OLTP path explicit, then override only transactions whose consistency contract justifies different blocking or retry behavior.","small":"Do not change transaction_read_only as a generic speed tweak. Higher isolation or long snapshots can amplify contention and vacuum pressure on a small node."},"mechanism":["transaction_read_only sets the current transaction's read-only status. It reflects the current transaction, begins from default_transaction_read_only, and must be set before operations that conflict with read-only mode.","transaction_read_only is session-settable but represents the current transaction; PostgreSQL restricts changes after the transaction has acquired a snapshot or performed conflicting work.","The default_* variables seed the corresponding transaction_* state. Isolation, read-only status, deferrability, retries, and snapshot lifetime must be designed together."],"pitfalls":["Changing transaction_read_only in one session and assuming role defaults, database defaults, or other pooled sessions changed with it.","Changing transaction semantics as a performance experiment and silently weakening an application's consistency contract.","Letting a pooled session retain transaction-related state because checkout or rollback/reset handling is incomplete.","Changing transaction_read_only globally without a rollback plan and a client or operational compatibility test."],"references":[{"title":"PostgreSQL 19 Beta 4: transaction_read_only","url":"https://www.postgresql.org/docs/19/runtime-config-client.html#GUC-TRANSACTION-READ-ONLY"},{"title":"PostgreSQL 19 release notes","url":"https://www.postgresql.org/docs/19/release-19.html"}],"related":["default_transaction_isolation","transaction_isolation","default_transaction_read_only","default_transaction_deferrable","transaction_deferrable"],"summary":"transaction_read_only is the PostgreSQL setting that defines the current transaction's read-only status."},"enumvals":[],"first_version":"9.0","group":"Client Connection Defaults","group_slug":"client","imported_at":"2026-09-27T17:57:32.23402+08:00","intro_commit":{},"key":"transaction_read_only","last_version":"20","max_val":"","min_val":"","name":"transaction_read_only","position":436,"present_in":["9.0","9.1","9.2","9.3","9.4","9.5","9.6","10","11","12","13","14","15","16","17","18","19","20"],"repair_provenance":{"original_source_revision":"english-manuals:bfd568fc8a9d915c53797166602b57c3df1db3a78725c09edbcea1df653f6dcf","receipt_sha256":"c7dae43961e91e95af894249d8aa1aba423bca89af72e59bcd51ac576648a2e5","repair":"wiki-repair-20261023"},"short_desc":"This parameter reflects the current transaction's read-only status.","short_desc_zh":"","source_rev":"wiki-repair-20261023:356447e8c507d14d0353c6d99bb01dd5e211e2ffe0c2d909ca80aee08e004470","unit":"","vartype":"bool"}},"Definition":{"Collection":"guc","Key":"transaction_read_only","SourceDatabase":"center","Version":"18","SourceTable":"guc","SourceKey":"transaction_read_only","SourceRevision":"wiki-repair-20261023:356447e8c507d14d0353c6d99bb01dd5e211e2ffe0c2d909ca80aee08e004470","Facts":{"boot_val":"off","category":"Client Connection Defaults / Statement Behavior","context":"user","description":"This parameter reflects the current transaction's read-only status. At the beginning of each transaction, it is set to the current value of default_transaction_read_only. Any subsequent attempt to change it is equivalent to a SET TRANSACTION command.","description_zh":"此参数反映当前事务的只读状态。在每个事务的开始，它被设置为 default_transaction_read_only 的当前值。任何后续更改它的尝试都等同于 SET TRANSACTION 命令。","description_zh_html":"\u003cp\u003e\n        此参数反映当前事务的只读状态。在每个事务的开始，它被设置为 \u003ca class=\"xref\" href=\"/zh/docs/18/runtime-config-client.html#GUC-DEFAULT-TRANSACTION-READ-ONLY\"\u003edefault_transaction_read_only\u003c/a\u003e 的当前值。任何后续更改它的尝试都等同于 \u003ca class=\"xref\" href=\"/zh/docs/18/sql-set-transaction.html\" title=\"SET TRANSACTION\"\u003e\u003cspan class=\"refentrytitle\"\u003eSET TRANSACTION\u003c/span\u003e\u003c/a\u003e 命令。\n       \u003c/p\u003e","doc":{"anchor":"GUC-TRANSACTION-READ-ONLY","file":"runtime-config-client.html","lang":"en","sha256":"6be6cc70f29eca4695dc43b2b2b94c75b7e0eaaa2c00273d7a98488917a7edb7","slug":"18"},"documented":true,"enumvals":null,"extra_desc":null,"lang":"en","max_val":null,"metadata_version":"18","min_val":null,"name":"transaction_read_only","short_desc":"Sets the current transaction's read-only status.","source":"pg-settings-source-snapshot","translation_provenance":{"inputs":[{"kind":"current-pgdoc-translation","path":"/Users/vonng/pgsty/pgdoc/zh/18/html/runtime-config-client.html","sha256":"1882f8fd5576909c4fcc44af53077378871e05f5be67723f20fe300273024767"}],"kind":"same-version-pgdoc","locale":"zh-Hans","source_revision":"b1b500221dbe5437cfca004d6b04d3f6e422765d","version":"18"},"unit":null,"vartype":"bool","zh_from":"same-version-pgdoc"},"ManualEvidence":{"doc":{"anchor":"GUC-TRANSACTION-READ-ONLY","file":"runtime-config-client.html","lang":"en","sha256":"6be6cc70f29eca4695dc43b2b2b94c75b7e0eaaa2c00273d7a98488917a7edb7","slug":"18"}},"MeasuredEvidence":{"metadata_version":"18"}},"Text":{"Collection":"guc","Key":"transaction_read_only","SourceDatabase":"center","Version":"18","Locale":"en","Title":"transaction_read_only","Summary":"This parameter reflects the current transaction's read-only status. At the beginning of each transaction, it is set to the current value of default_transaction_read_only. Any subsequent attempt to change it is equivalent to a SET TRANSACTION command.","BodyHTML":"\u003cp\u003eThis parameter reflects the current transaction\u0026#39;s read-only status. At the beginning of each transaction, it is set to the current value of default_transaction_read_only. Any subsequent attempt to change it is equivalent to a SET TRANSACTION command.\u003c/p\u003e","SourceRevision":"wiki-repair-20261023:356447e8c507d14d0353c6d99bb01dd5e211e2ffe0c2d909ca80aee08e004470","ContentHash":"69127e65becf9888149980b3a2edf976c38e206659cdeac3ee838bf17f12a431","Payload":{"description":"This parameter reflects the current transaction's read-only status. At the beginning of each transaction, it is set to the current value of default_transaction_read_only. 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