42P04 — 重复数据库

集群中已存在同名数据库。

英文手册覆盖始于 PostgreSQL 8.1. 来源历史与运行验证各自保留独立版本边界。

当前阅读 PG 18·选择有来源记录的版本

8.1 8.2 8.3 8.4 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

aliases: 未知
class name: Syntax Error or Access Rule Violation
condition name: duplicate_database
lang: en
sqlstate: 42P04

版本定义 PG 18

42P04 — 重复数据库

速览 {#at-a-glance}

42P04（duplicate_database）表示数据库管理路径发现集群中已有同名数据库。这是集群级名称检查，不是当前库内的关系冲突；CREATE 和 RENAME 的外围检查也不同。

含义 {#meaning}

createdb 会用 get_database_oid(dbname, true) 检查目标名称，冲突时报告 ERROR database "%s" already exists。RenameDatabase 在查找旧数据库、检查所有权和 CREATEDB 权限之后，对 newname 做同样检查。因此 %s 在 CREATE 中是请求的数据库名，在 RENAME 中是新名称。

utility 分发器在进入 createdb 前调用 PreventInTransactionBlock(isTopLevel, "CREATE DATABASE")。所以在显式事务中执行 CREATE DATABASE 是另一种事务块错误，不能据此声称发出了 42P04；RENAME 则有独立的旧名、所有权、权限和新名检查。

诊断 {#diagnosis}

确认目标集群和准确名称，检查 pg_database、标识符折叠和迁移竞争。CREATE 另查目标名称、模板和所有者前提；RENAME 同时查旧名、新名、所有权和 CREATEDB。旧数据库不存在或权限不足不应误判为 42P04。

处理 {#response}

已有库就是目标时让编排幂等并检查它；否则选择未占用名称。CREATE DATABASE 要在顶层、显式事务块之外执行。RENAME 只有在确认旧库、所有权、CREATEDB、活动会话、依赖和集群身份后才选择可用新名。如果 RENAME 在显式事务中报错，下一条命令前应执行 ROLLBACK；若必须保留外层事务，则回滚到改名前建立的保存点。删除或改名不是所有 42P04 的通用修复。

消息变体 {#messages}

选定路径均为 ERROR database "%s" already exists：createdb 使用请求名称，RenameDatabase 使用新名称。utility 中的 PreventInTransactionBlock 证明 CREATE DATABASE 有独立事务限制，不是另一条 42P04 报文。

版本 {#versions}

目录范围从 7.4 到 18.6、19beta3，不是精确的功能引入判断。选定的是 18.6 固定 CREATE、RENAME 和分发器事务检查路径，未运行数据库。

来源 {#sources}

src.errcodes.42P04.18.6 — src/backend/utils/errcodes.txt line 379，固定于 724edf9bde9d356724ad384a2e196edc3c9f80f7；SHA-256 6e8de346643ba84aa3c9c6a73360acfc7b2dfb89162c06c08ce9bf5bcd5bbcba（源码）。
src.call.42P04.465a77b5605c341bc91f6990 — src/backend/commands/dbcommands.c lines 1393-1395，固定于 724edf9bde9d356724ad384a2e196edc3c9f80f7；SHA-256 64b77d2197dce16eb1ad19d8168382459d621a03df0b00be157f7db39ca22acf（源码）。
src.call.42P04.b0d1644def83c14a7504fec4 — src/backend/commands/dbcommands.c lines 1949-1951，固定于 724edf9bde9d356724ad384a2e196edc3c9f80f7；SHA-256 64b77d2197dce16eb1ad19d8168382459d621a03df0b00be157f7db39ca22acf（源码）。
src.call.42P04.create-tx-guard — src/backend/tcop/utility.c lines 769-773，固定于 724edf9bde9d356724ad384a2e196edc3c9f80f7；SHA-256 7aae5d07628b6debf8456d1d4ea96f28912232192e56ea25773b4c4b61235a00（源码）。
src.calls.REL_18_6.42P04 — 固定本地核心调用扫描；SHA-256 9ee8a0e81d8f0825c5c1ae45583439859a26e602bdd4ce2f2a62aa278867ccbf。
作者证据 — 记录源码断言、消息角色和运行边界。

比较版本

SQLSTATE 证据与已记录的运行版本

claims · identity.class-and-condition

{
  "claim_id": "identity.class-and-condition",
  "limits": "Identity does not enumerate all source branches or client failures.",
  "method": "Read fixed REL_18_6 errcodes.txt and locked facts.",
  "position": 0,
  "runtime": [],
  "sources": [
    "src.errcodes.42P04.18.6"
  ],
  "statement": "42P04 is the duplicate_database condition in Class 42."
}

claims · mechanism.selected-source-path

{
  "claim_id": "mechanism.selected-source-path",
  "limits": "Representative confirmed core paths only; not exhaustive historical or extension coverage.",
  "method": "Read complete resolved REL_18_6 report groups and message roles.",
  "position": 1,
  "runtime": [],
  "sources": [
    "src.call.42P04.465a77b5605c341bc91f6990",
    "src.call.42P04.b0d1644def83c14a7504fec4",
    "src.call.42P04.create-tx-guard"
  ],
  "statement": "createdb checks the requested database name and RenameDatabase checks newname after old-database ownership and CREATEDB checks; both report ERROR `database \"%s\" already exists`. The utility dispatcher separately calls PreventInTransactionBlock for CREATE DATABASE before createdb, so an explicit transaction-block failure is not 42P04."
}

claims · versions.catalogue-boundary

{
  "claim_id": "versions.catalogue-boundary",
  "limits": "First observed release is a lower bound, not precise behavioral introduction.",
  "method": "Read locked catalogue facts and definition snapshots.",
  "position": 2,
  "runtime": [],
  "sources": [
    "src.errcodes.42P04.18.6"
  ],
  "statement": "From 7.4 through 18.6 and 19beta3; this catalogue range is not a precise introduction claim. The selected CREATE, RENAME, and dispatcher guards are fixed 18.6 source paths and no runtime case was run."
}

messages · message.variant-1

{
  "limits": "Placeholders remain dynamic source fields; no concrete runtime value is claimed.",
  "message_id": "message.variant-1",
  "path": "",
  "position": 0,
  "raw": {
    "detail_templates": [],
    "hint_templates": [],
    "id": "message.variant-1",
    "limits": "Placeholders remain dynamic source fields; no concrete runtime value is claimed.",
    "primary_template": "database \"%s\" already exists",
    "roles": [
      {
        "role": "errmsg",
        "template": "database \"%s\" already exists"
      }
    ],
    "severity_source": "explicit ERROR",
    "sources": [
      "src.call.42P04.465a77b5605c341bc91f6990"
    ],
    "sqlstate": "42P04"
  },
  "severity": "explicit ERROR",
  "sources": [
    "src.call.42P04.465a77b5605c341bc91f6990"
  ],
  "templates": [
    {
      "kind": "primary",
      "literal": "database \" \" already exists",
      "position": 0,
      "role": "",
      "template": "database \"%s\" already exists"
    }
  ]
}

messages · message.variant-2

{
  "limits": "Placeholders remain dynamic source fields; no concrete runtime value is claimed.",
  "message_id": "message.variant-2",
  "path": "",
  "position": 1,
  "raw": {
    "detail_templates": [],
    "hint_templates": [],
    "id": "message.variant-2",
    "limits": "Placeholders remain dynamic source fields; no concrete runtime value is claimed.",
    "primary_template": "database \"%s\" already exists",
    "roles": [
      {
        "role": "errmsg",
        "template": "database \"%s\" already exists"
      }
    ],
    "severity_source": "explicit ERROR",
    "sources": [
      "src.call.42P04.b0d1644def83c14a7504fec4"
    ],
    "sqlstate": "42P04"
  },
  "severity": "explicit ERROR",
  "sources": [
    "src.call.42P04.b0d1644def83c14a7504fec4"
  ],
  "templates": [
    {
      "kind": "primary",
      "literal": "database \" \" already exists",
      "position": 0,
      "role": "",
      "template": "database \"%s\" already exists"
    }
  ]
}

sources · src.errcodes.42P04.18.6

{
  "commit": "724edf9bde9d356724ad384a2e196edc3c9f80f7",
  "docs_url": "",
  "kind": "upstream_source",
  "location": "line 379",
  "path": "src/backend/utils/errcodes.txt",
  "position": 0,
  "sha256": "6e8de346643ba84aa3c9c6a73360acfc7b2dfb89162c06c08ce9bf5bcd5bbcba",
  "source_id": "src.errcodes.42P04.18.6",
  "tag": "REL_18_6",
  "url": "https://github.com/postgres/postgres/blob/724edf9bde9d356724ad384a2e196edc3c9f80f7/src/backend/utils/errcodes.txt#L379"
}

sources · src.call.42P04.465a77b5605c341bc91f6990

{
  "commit": "724edf9bde9d356724ad384a2e196edc3c9f80f7",
  "docs_url": "",
  "kind": "upstream_source",
  "location": "lines 1393-1395",
  "path": "src/backend/commands/dbcommands.c",
  "position": 1,
  "sha256": "64b77d2197dce16eb1ad19d8168382459d621a03df0b00be157f7db39ca22acf",
  "source_id": "src.call.42P04.465a77b5605c341bc91f6990",
  "tag": "REL_18_6",
  "url": "https://github.com/postgres/postgres/blob/724edf9bde9d356724ad384a2e196edc3c9f80f7/src/backend/commands/dbcommands.c#L1393-L1395"
}

sources · src.call.42P04.b0d1644def83c14a7504fec4

{
  "commit": "724edf9bde9d356724ad384a2e196edc3c9f80f7",
  "docs_url": "",
  "kind": "upstream_source",
  "location": "lines 1949-1951",
  "path": "src/backend/commands/dbcommands.c",
  "position": 2,
  "sha256": "64b77d2197dce16eb1ad19d8168382459d621a03df0b00be157f7db39ca22acf",
  "source_id": "src.call.42P04.b0d1644def83c14a7504fec4",
  "tag": "REL_18_6",
  "url": "https://github.com/postgres/postgres/blob/724edf9bde9d356724ad384a2e196edc3c9f80f7/src/backend/commands/dbcommands.c#L1949-L1951"
}

sources · src.call.42P04.create-tx-guard

{
  "commit": "724edf9bde9d356724ad384a2e196edc3c9f80f7",
  "docs_url": "",
  "kind": "upstream_source",
  "location": "lines 769-773",
  "path": "src/backend/tcop/utility.c",
  "position": 3,
  "sha256": "7aae5d07628b6debf8456d1d4ea96f28912232192e56ea25773b4c4b61235a00",
  "source_id": "src.call.42P04.create-tx-guard",
  "tag": "REL_18_6",
  "url": "https://github.com/postgres/postgres/blob/724edf9bde9d356724ad384a2e196edc3c9f80f7/src/backend/tcop/utility.c#L769-L773"
}

sources · src.calls.REL_18_6.42P04

{
  "commit": "",
  "docs_url": "",
  "kind": "local_artifact",
  "location": "",
  "path": "raw/calls/REL_18_6.jsonl",
  "position": 4,
  "sha256": "9ee8a0e81d8f0825c5c1ae45583439859a26e602bdd4ce2f2a62aa278867ccbf",
  "source_id": "src.calls.REL_18_6.42P04",
  "tag": "",
  "url": ""
}

来源引用

原始手册引用

完整定义与证据 JSON

定义来源

center · PostgreSQL 18 · english-manuals:f1db4505ca7b2febec41002e678784e5ca3205000b2f242e3a94549651fe8102

正文语言: zh-Hans · english-manuals:f1db4505ca7b2febec41002e678784e5ca3205000b2f242e3a94549651fe8102

42P04 — 重复数据库

版本定义 PG 18

42P04 — 重复数据库

速览 {#at-a-glance}

含义 {#meaning}

诊断 {#diagnosis}

处理 {#response}

消息变体 {#messages}

版本 {#versions}

相关 {#related}

来源 {#sources}

比较版本

SQLSTATE 证据与已记录的运行版本

来源引用