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系統目錄（system catalog）是記錄資料庫管理系統儲存結構原始資料的地方，例如關於資料表和欄位的訊息以及內部日誌記錄訊息。PostgreSQL 的系統目錄是一般的資料表。您可以刪除並重新建立資料表、增加欄位、插入和更新內容，並以這種方式嚴重混淆您的系統。當然，通常情況下，不應該手動更改系統目錄，通常有 SQL 命令來執行此操作。（例如，CREATE DATABASE 向 pg_database 系統目錄插入一行 - 實際上是在磁碟上建立數據庫）。對於特別深奧的操作有一些例外，但其中很多已經隨著時間的推移而變為 SQL 命令，因此需要系統目錄的直接操作正在不斷減少。
The catalog pg_attribute stores information about table columns. There will be exactly one pg_attribute row for every column in every table in the database. (There will also be attribute entries for indexes, and indeed all objects that have pg_class entries.)
The term attribute is equivalent to column and is used for historical reasons.
pg_attribute ColumnsIn a dropped column's pg_attribute entry, atttypid is reset to zero, but attlen and the other fields copied from pg_type are still valid. This arrangement is needed to cope with the situation where the dropped column's data type was later dropped, and so there is no pg_type row anymore. attlen and the other fields can be used to interpret the contents of a row of the table.
.oid
The data type of this column
attstattarget
int4
attstattarget controls the level of detail of statistics accumulated for this column by . A zero value indicates that no statistics should be collected. A negative value says to use the system default statistics target. The exact meaning of positive values is data type-dependent. For scalar data types, attstattarget is both the target number of “most common values” to collect, and the target number of histogram bins to create.
attlen
int2
A copy of pg_type.typlen of this column's type
attnum
int2
The number of the column. Ordinary columns are numbered from 1 up. System columns, such as oid, have (arbitrary) negative numbers.
attndims
int4
Number of dimensions, if the column is an array type; otherwise 0. (Presently, the number of dimensions of an array is not enforced, so any nonzero value effectively means “it's an array”.)
attcacheoff
int4
Always -1 in storage, but when loaded into a row descriptor in memory this might be updated to cache the offset of the attribute within the row
atttypmod
int4
atttypmod records type-specific data supplied at table creation time (for example, the maximum length of a varchar column). It is passed to type-specific input functions and length coercion functions. The value will generally be -1 for types that do not need atttypmod.
attbyval
bool
A copy of pg_type.typbyval of this column's type
attstorage
char
Normally a copy of pg_type.typstorage of this column's type. For TOAST-able data types, this can be altered after column creation to control storage policy.
attalign
char
A copy of pg_type.typalign of this column's type
attnotnull
bool
This represents a not-null constraint.
atthasdef
bool
This column has a default value, in which case there will be a corresponding entry in the pg_attrdef catalog that actually defines the value.
attidentity
char
If a zero byte (''), then not an identity column. Otherwise, a = generated always, d = generated by default.
attisdropped
bool
This column has been dropped and is no longer valid. A dropped column is still physically present in the table, but is ignored by the parser and so cannot be accessed via SQL.
attislocal
bool
This column is defined locally in the relation. Note that a column can be locally defined and inherited simultaneously.
attinhcount
int4
The number of direct ancestors this column has. A column with a nonzero number of ancestors cannot be dropped nor renamed.
attcollation
oid
.oid
The defined collation of the column, or zero if the column is not of a collatable data type.
attacl
aclitem[]
Column-level access privileges, if any have been granted specifically on this column
attoptions
text[]
Attribute-level options, as “keyword=value” strings
attfdwoptions
text[]
Attribute-level foreign data wrapper options, as “keyword=value” strings
attrelid
oid
pg_class.oid
The table this column belongs to
attname
name
The column name
atttypid
oid
目錄 pg_subscription 包含所有現有訂閱的邏輯複寫。有關邏輯複寫的相關資訊，請參閱第 30 章。
與大多數系統目錄不同，pg_subscription 在叢集的所有資料庫之間是共享的：每個叢集只有一個 pg_subscription，而不是每個資料庫一個。
普通使用者沒有權限讀取 subconninfo 欄位，因為該欄位可能包含純文字密碼。
pg_subscription ColumnsThe catalog pg_am stores information about relation access methods. There is one row for each access method supported by the system. Currently, only tables and indexes have access methods. The requirements for table and index access methods are discussed in detail in and respectively.
pg_am Columns目錄 pg_auth_members 顯示角色之間的成員資格關連。允許任何非循環的關連。
由於角色身份是叢集範圍的，因此 pg_auth_members 在叢集的所有資料庫之間共享：每個叢集只有一個 pg_auth_members 副本，而不是每個資料庫一個副本。
Table 51.9. pg_auth_members Columns
The pg_replication_origin_status view contains information about how far replay for a certain origin has progressed. For more on replication origins see .
Table 51.80. pg_replication_origin_status Columns
Column Type
Description
oid oid
Row identifier
subdbid oid (references pg_database.oid)
OID of the database which the subscription resides in
subname name
Name of the subscription
subowner oid (references pg_authid.oid)
Owner of the subscription
subenabled bool
If true, the subscription is enabled and should be replicating.
subconninfo text
Connection string to the upstream database
subslotname name
Name of the replication slot in the upstream database (also used for the local replication origin name); null represents NONE
subsynccommit text
Contains the value of the synchronous_commit setting for the subscription workers.
subpublications text[]
Array of subscribed publication names. These reference the publications on the publisher server. For more on publications see Section 30.1.
name
name
Extension name
default_version
text
預設版本的名稱；如果未指定，則為 NULL
installed_version
text
目前安裝的延伸功能版本，如果未安裝，則為 NULL
comment
text
延伸功能的控制檔案中的註解文字內容
pg_available_extensions 檢視表是唯讀的。
oid oid
Row identifier
amname name
Name of the access method
amhandler regproc (references .oid)
OID of a handler function that is responsible for supplying information about the access method
amtype char
t = table (including materialized views), i = index.
Before PostgreSQL 9.6, pg_am contained many additional columns representing properties of index access methods. That data is now only directly visible at the C code level. However, pg_index_column_has_property() and related functions have been added to allow SQL queries to inspect index access method properties; see Table 9.71.
Column Type
Description
srsubid oid (references .oid)
Reference to subscription
srrelid oid (references .oid)
Reference to relation
srsubstate char
State code: i = initialize, d = data is being copied, s = synchronized, r = ready (normal replication)
srsublsn pg_lsn
Remote LSN of the state change used for synchronization coordination when in s or r states, otherwise null
Column Type
Description
``.oid
具有成員的角色 ID
member
oid
.oid
作為 roleid 成員的角色 ID
grantor
oid
``.oid
授予此成員資格的角色 ID
admin_option
bool
如果成員可以將 roleid 的成員資格授予其他人，則為 True
roleid
oid
.roident
internal node identifier
external_id
text
.roname
external node identifier
remote_lsn
pg_lsn
The origin node's LSN up to which data has been replicated.
local_lsn
pg_lsn
This node's LSN at which remote_lsn has been replicated. Used to flush commit records before persisting data to disk when using asynchronous commits.
local_id
Oid
系統目錄 pg_cast 儲存資料型別的轉換方式，包括了內建的和使用者定義的。
需要注意的是，pg_cast 並不代表系統知道如何執行的每一種型別轉換；只有那些不能從某些通用規則中推導出來的。例如，domain 和它的基本型別之間的轉換在 pg_cast 中就沒有明確表示。另一個重要的例外是「自動 I/O 強制轉換」，即使用資料型別自己的 I/O 函數執行的轉換為 text 或其他字串型別或從 text 及其他字串型別轉換的那些，在 pg_cast 中沒有明確表示。
pg_cast ColumnsColumn Type
Description
The cast functions listed in pg_cast must always take the cast source type as their first argument type, and return the cast destination type as their result type. A cast function can have up to three arguments. The second argument, if present, must be type integer; it receives the type modifier associated with the destination type, or -1 if there is none. The third argument, if present, must be type boolean; it receives true if the cast is an explicit cast, false otherwise.
It is legitimate to create a pg_cast entry in which the source and target types are the same, if the associated function takes more than one argument. Such entries represent “length coercion functions” that coerce values of the type to be legal for a particular type modifier value.
When a pg_cast entry has different source and target types and a function that takes more than one argument, it represents converting from one type to another and applying a length coercion in a single step. When no such entry is available, coercion to a type that uses a type modifier involves two steps, one to convert between data types and a second to apply the modifier.
版本：11
The catalog pg_statistic_ext holds definitions of extended planner statistics. Each row in this catalog corresponds to a statistics object created with CREATE STATISTICS.
pg_statistic_ext ColumnsThe pg_statistic_ext entry is filled in completely during CREATE STATISTICS, but the actual statistical values are not computed then. Subsequent ANALYZE commands compute the desired values and populate an entry in the catalog.
The view pg_hba_file_rules provides a summary of the contents of the client authentication configuration file, pg_hba.conf. A row appears in this view for each non-empty, non-comment line in the file, with annotations indicating whether the rule could be applied successfully.
This view can be helpful for checking whether planned changes in the authentication configuration file will work, or for diagnosing a previous failure. Note that this view reports on the current contents of the file, not on what was last loaded by the server.
By default, the pg_hba_file_rules view can be read only by superusers.
pg_hba_file_rules ColumnsUsually, a row reflecting an incorrect entry will have values for only the line_number and error fields.
使用者身份驗證設定的相關資訊，請參閱。
The view pg_prepared_xacts displays information about transactions that are currently prepared for two-phase commit (see PREPARE TRANSACTION for details).
pg_prepared_xacts contains one row per prepared transaction. An entry is removed when the transaction is committed or rolled back.
pg_prepared_xacts ColumnsWhen the pg_prepared_xacts view is accessed, the internal transaction manager data structures are momentarily locked, and a copy is made for the view to display. This ensures that the view produces a consistent set of results, while not blocking normal operations longer than necessary. Nonetheless there could be some impact on database performance if this view is frequently accessed.
The catalog pg_tablespace stores information about the available tablespaces. Tables can be placed in particular tablespaces to aid administration of disk layout.
Unlike most system catalogs, pg_tablespace is shared across all databases of a cluster: there is only one copy of pg_tablespace per cluster, not one per database.
pg_tablespace ColumnsThe catalog pg_event_trigger stores event triggers. See Chapter 39 for more information.
pg_event_trigger ColumnsColumn Type
Description
The catalog pg_opclass defines index access method operator classes. Each operator class defines semantics for index columns of a particular data type and a particular index access method. An operator class essentially specifies that a particular operator family is applicable to a particular indexable column data type. The set of operators from the family that are actually usable with the indexed column are whichever ones accept the column's data type as their left-hand input.
Operator classes are described at length in .
Table 51.33. pg_opclass Columns
Row identifier (hidden attribute; must be explicitly selected)
rulename
name
Rule name
ev_class
oid
pg_class.oid
The table this rule is for
ev_type
char
Event type that the rule is for: 1 = SELECT, 2 = UPDATE, 3 = INSERT, 4 = DELETE
ev_enabled
char
Controls in which session_replication_role modes the rule fires. O = rule fires in “origin” and “local” modes, D = rule is disabled, R = rule fires in “replica” mode, A = rule fires always.
is_instead
bool
True if the rule is an INSTEAD rule
ev_qual
pg_node_tree
Expression tree (in the form of a nodeToString() representation) for the rule's qualifying condition
ev_action
pg_node_tree
Query tree (in the form of a nodeToString() representation) for the rule's action
oid oid
Row identifier
castsource oid (references pg_type.oid)
OID of the source data type
casttarget oid (references pg_type.oid)
OID of the target data type
castfunc oid (references pg_proc.oid)
The OID of the function to use to perform this cast. Zero is stored if the cast method doesn't require a function.
castcontext char
Indicates what contexts the cast can be invoked in. e means only as an explicit cast (using CAST or :: syntax). a means implicitly in assignment to a target column, as well as explicitly. i means implicitly in expressions, as well as the other cases.
castmethod char
Indicates how the cast is performed. f means that the function specified in the castfunc field is used. i means that the input/output functions are used. b means that the types are binary-coercible, thus no conversion is required.
Column Type
Description
transaction xid
Numeric transaction identifier of the prepared transaction
gid text
Global transaction identifier that was assigned to the transaction
prepared timestamptz
Time at which the transaction was prepared for commit
owner name (references pg_authid.rolname)
Name of the user that executed the transaction
database name (references pg_database.datname)
Name of the database in which the transaction was executed
Column Type
Description
oid oid
Row identifier
spcname name
Tablespace name
spcowner oid (references pg_authid.oid)
Owner of the tablespace, usually the user who created it
spcacl aclitem[]
Access privileges; see Section 5.7 for details
spcoptions text[]
Tablespace-level options, as “keyword=value” strings
oid oid
Row identifier
evtname name
Trigger name (must be unique)
evtevent name
Identifies the event for which this trigger fires
evtowner oid (references pg_authid.oid)
Owner of the event trigger
evtfoid oid (references pg_proc.oid)
The function to be called
evtenabled char
Controls in which session_replication_role modes the event trigger fires. O = trigger fires in “origin” and “local” modes, D = trigger is disabled, R = trigger fires in “replica” mode, A = trigger fires always.
evttags text[]
Command tags for which this trigger will fire. If NULL, the firing of this trigger is not restricted on the basis of the command tag.
Column Type
Description
oid oid
Row identifier
stxrelid oid (references pg_class.oid)
Table containing the columns described by this object
stxname name
Name of the statistics object
stxnamespace oid (references pg_namespace.oid)
The OID of the namespace that contains this statistics object
stxowner oid (references pg_authid.oid)
Owner of the statistics object
stxstattarget int4
stxstattarget controls the level of detail of statistics accumulated for this statistics object by ANALYZE. A zero value indicates that no statistics should be collected. A negative value says to use the maximum of the statistics targets of the referenced columns, if set, or the system default statistics target. Positive values of stxstattarget determine the target number of “most common values” to collect.
stxkeys int2vector (references pg_attribute.attnum)
An array of attribute numbers, indicating which table columns are covered by this statistics object; for example a value of 1 3 would mean that the first and the third table columns are covered
stxkind char[]
An array containing codes for the enabled statistic kinds; valid values are: d for n-distinct statistics, f for functional dependency statistics, and m for most common values (MCV) list statistics
Column Type
Description
line_number int4
Line number of this rule in pg_hba.conf
type text
Type of connection
database text[]
List of database name(s) to which this rule applies
user_name text[]
List of user and group name(s) to which this rule applies
address text
Host name or IP address, or one of all, samehost, or samenet, or null for local connections
netmask text
IP address mask, or null if not applicable
auth_method text
Authentication method
options text[]
Options specified for authentication method, if any
error text
If not null, an error message indicating why this line could not be processed
tablename name (references pg_class.relname)
Name of table the index is for
indexname name (references pg_class.relname)
Name of index
tablespace name (references pg_tablespace.spcname)
Name of tablespace containing index (null if default for database)
indexdef text
Index definition (a reconstructed CREATE INDEX command)
oid
oid
Row identifier (hidden attribute; must be explicitly selected)
opcmethod
oid
.oid
Index access method operator class is for
opcname
name
Name of this operator class
opcnamespace
oid
.oid
An operator class's opcmethod must match the opfmethod of its containing operator family. Also, there must be no more than one pg_opclass row having opcdefault true for any given combination of opcmethod and opcintype.
name
name
延伸功能名稱
version
text
版本名稱
installed
bool
如果目前已安裝此延伸功能的此版本，則為 True
superuser
bool
如果僅允許超級使用者安裝此延伸功能，則為 True
relocatable
bool
pg_available_extension_versions 檢視表是唯讀的。
The catalog pg_collation describes the available collations, which are essentially mappings from an SQL name to operating system locale categories. See Section 23.2 for more information.
Table 51.12. pg_collation Columns
oid
Note that the unique key on this catalog is (collname, collencoding, collnamespace) not just (collname, collnamespace). PostgreSQL generally ignores all collations that do not have collencoding equal to either the current database's encoding or -1, and creation of new entries with the same name as an entry with collencoding = -1 is forbidden. Therefore it is sufficient to use a qualified SQL name (schema.name) to identify a collation, even though this is not unique according to the catalog definition. The reason for defining the catalog this way is that initdb fills it in at cluster initialization time with entries for all locales available on the system, so it must be able to hold entries for all encodings that might ever be used in the cluster.
In the template0 database, it could be useful to create collations whose encoding does not match the database encoding, since they could match the encodings of databases later cloned from template0. This would currently have to be done manually.
The catalog pg_policy stores row level security policies for tables. A policy includes the kind of command that it applies to (possibly all commands), the roles that it applies to, the expression to be added as a security-barrier qualification to queries that include the table, and the expression to be added as a WITH CHECK option for queries that attempt to add new records to the table.
Table 51.38. pg_policy Columns
Policies stored in pg_policy are applied only when pg_class.relrowsecurity is set for their table.
The catalog pg_statistic stores statistical data about the contents of the database. Entries are created by and subsequently used by the query planner. Note that all the statistical data is inherently approximate, even assuming that it is up-to-date.
Normally there is one entry, with stainherit = false, for each table column that has been analyzed. If the table has inheritance children, a second entry with stainherit = true is also created. This row represents the column's statistics over the inheritance tree, i.e., statistics for the data you'd see with SELECT column FROM table*, whereas the stainherit
The catalog pg_authid contains information about database authorization identifiers (roles). A role subsumes the concepts of “users” and “groups”. A user is essentially just a role with the rolcanlogin flag set. Any role (with or without rolcanlogin) can have other roles as members; see .
Since this catalog contains passwords, it must not be publicly readable. is a publicly readable view on pg_authid that blanks out the password field.
contains detailed information about user and privilege management.
Because user identities are cluster-wide, pg_authid is shared across all databases of a cluster: there is only one copy of pg_authid
如果延伸功能可以接受重新定位到另一個綱要，則為 True
schema
name
延伸功能必須安裝到的綱要名稱，如果可部分或完全重新定位，則為 NULL
requires
name[]
必須預先安裝的延伸功能名稱，如果沒有則為 NULL
comment
text
延伸功能控制檔案中的註解文字內容
oid
Row identifier (hidden attribute; must be explicitly selected)
collname
name
Collation name (unique per namespace and encoding)
collnamespace
oid
pg_namespace.oid
The OID of the namespace that contains this collation
collowner
oid
pg_authid.oid
Owner of the collation
collprovider
char
Provider of the collation: d = database default, c = libc, i = icu
collencoding
int4
Encoding in which the collation is applicable, or -1 if it works for any encoding
collcollate
name
LC_COLLATE for this collation object
collctype
name
LC_CTYPE for this collation object
collversion
text
Provider-specific version of the collation. This is recorded when the collation is created and then checked when it is used, to detect changes in the collation definition that could lead to data corruption.
polname
name
The name of the policy
polrelid
oid
pg_class.oid
The table to which the policy applies
polcmd
char
The command type to which the policy is applied: r for SELECT, a for INSERT, w for UPDATE, d for DELETE, or * for all
polpermissive
boolean
Is the policy permissive or restrictive?
polroles
oid[]
pg_authid.oid
The roles to which the policy is applied
polqual
pg_node_tree
The expression tree to be added to the security barrier qualifications for queries that use the table
polwithcheck
pg_node_tree
The expression tree to be added to the WITH CHECK qualifications for queries that attempt to add rows to the table
Namespace of this operator class
opcowner
oid
pg_authid.oid
Owner of the operator class
opcfamily
oid
pg_opfamily.oid
Operator family containing the operator class
opcintype
oid
pg_type.oid
Data type that the operator class indexes
opcdefault
bool
True if this operator class is the default for opcintype
opckeytype
oid
pg_type.oid
Type of data stored in index, or zero if same as opcintype
falseSELECT columntablepg_statistic also stores statistical data about the values of index expressions. These are described as if they were actual data columns; in particular, starelid references the index. No entry is made for an ordinary non-expression index column, however, since it would be redundant with the entry for the underlying table column. Currently, entries for index expressions always have stainherit = false.
Since different kinds of statistics might be appropriate for different kinds of data, pg_statistic is designed not to assume very much about what sort of statistics it stores. Only extremely general statistics (such as nullness) are given dedicated columns in pg_statistic. Everything else is stored in “slots”, which are groups of associated columns whose content is identified by a code number in one of the slot's columns. For more information see src/include/catalog/pg_statistic.h.
pg_statistic should not be readable by the public, since even statistical information about a table's contents might be considered sensitive. (Example: minimum and maximum values of a salary column might be quite interesting.) pg_stats is a publicly readable view on pg_statistic that only exposes information about those tables that are readable by the current user.
Column Type
Description
starelid oid (references .oid)
The table or index that the described column belongs to
staattnum int2 (references .attnum)
The number of the described column
stainherit bool
If true, the stats include inheritance child columns, not just the values in the specified relation
stanullfrac float4
The fraction of the column's entries that are null
stawidth int4
The average stored width, in bytes, of nonnull entries
stadistinct float4
The number of distinct nonnull data values in the column. A value greater than zero is the actual number of distinct values. A value less than zero is the negative of a multiplier for the number of rows in the table; for example, a column in which about 80% of the values are nonnull and each nonnull value appears about twice on average could be represented by stadistinct = -0.4. A zero value means the number of distinct values is unknown.
stakindN int2
A code number indicating the kind of statistics stored in the Nth “slot” of the pg_statistic row.
staopN oid (references .oid)
An operator used to derive the statistics stored in the Nth “slot”. For example, a histogram slot would show the < operator that defines the sort order of the data.
stacollN oid (references .oid)
The collation used to derive the statistics stored in the Nth “slot”. For example, a histogram slot for a collatable column would show the collation that defines the sort order of the data. Zero for noncollatable data.
Column Type
Description
oid oid
Row identifier
rolname name
Role name
rolsuper bool
Role has superuser privileges
rolinherit bool
Role automatically inherits privileges of roles it is a member of
rolcreaterole bool
Role can create more roles
rolcreatedb bool
Role can create databases
rolcanlogin bool
Role can log in. That is, this role can be given as the initial session authorization identifier
rolreplication bool
Role is a replication role. A replication role can initiate replication connections and create and drop replication slots.
rolbypassrls bool
Role bypasses every row level security policy, see for more information.
For an MD5 encrypted password, rolpassword column will begin with the string md5 followed by a 32-character hexadecimal MD5 hash. The MD5 hash will be of the user's password concatenated to their user name. For example, if user joe has password xyzzy, PostgreSQL will store the md5 hash of xyzzyjoe.
If the password is encrypted with SCRAM-SHA-256, it has the format:
where salt, StoredKey and ServerKey are in Base64 encoded format. This format is the same as that specified by RFC 5803.
A password that does not follow either of those formats is assumed to be unencrypted.
目錄 pg_database 儲存有關資料庫一些可用的訊息。資料庫是使用 CREATE DATABASE 命令建立的。關於某些參數的含義的詳細訊息，請參閱第 22 章。
與大多數系統目錄不同，pg_database 在叢集的所有資料庫之間共享：每個叢集只有一個 pg_database 副本，而不是每個資料庫一個副本。
Table 51.15. pg_database 欄位
oid
版本：11
目錄 pg_language 註冊了可以撰寫函數或 stored procedure 的語言。有關語言處理程序的更多訊息，請參閱 CREATE LANGUAGE 和第 41 章。
pg_language Columns目錄 pg_extension 儲存有關已安裝延伸功能的資訊。有關延伸功能的詳細資訊，請參閱第 37.17 節。
Table 51.22. pg_extension Columns
oid
oid
請注意，與大多數帶有「namespace」欄位的目錄不同，extnamespace 並不暗指該延伸功能屬於該綱要(schema)。延伸功能並不在任何綱要之中。不過 extnamespace 指示包含大多數或所有延伸功能所屬物件的綱要。如果 extrelocatable 為 true，則此綱要實際上必須包含屬於該延伸功能的所有需要綱要的物件。\
SCRAM-SHA-256$<iteration count>:<salt>$<StoredKey>:<ServerKey>oid
資料列識別指標（隱藏屬性；必須明確選擇）
datname
name
資料庫名稱
datdba
oid
pg_authid.oid
資料庫的擁有者，通常是建立它的使用者
encoding
int4
此資料庫的字元編碼（pg_encoding_to_char（）可將此數字轉換為編碼名稱）
datcollate
name
這個資料庫的 LC_COLLATE
datctype
name
這個資料庫的 LC_CTYPE
datistemplate
bool
如果為 true，則該資料庫可以由具有 CREATEDB 權限的任何使用者複製；如果為 false，則只有超級使用者或資料庫的擁有者才能複製它。
datallowconn
bool
如果為 false，則沒有人可以連線到該資料庫。這用於保護 template0 資料庫免遭更改。
datconnlimit
int4
設定可以對此資料庫執行的最大同時連線數。-1 意味著沒有限制。
datlastsysoid
oid
資料庫中的最後一個系統 OID；特別適用於 pg_dump
datfrozenxid
xid
在這個事務 ID 之前在此資料庫中的所有事務 ID，已被替換為永久（「 frozen」）。這用於追踪是否需要清理資料庫以防止事務 ID 重覆或允許縮減 pg_xact。它是每個資料表 pg_class.relfrozenxid 的最小值。
datminmxid
xid
此資料庫中的所有 multixact ID 已被替換為該資料庫中的事務 ID。這用於追踪資料庫是否需要清理，以防止 multixact ID 重覆或允許縮減 pg_multixact。它是每個資料表 pg_class.relminmxid 的最小值。
dattablespace
oid
pg_tablespace.oid
資料庫預設的資料表空間。在此資料庫中，pg_class.reltablespace 為零的所有資料表都將儲存在此資料表空間中；特別是所有非共享系統目錄都將在那裡。
datacl
aclitem[]
資料列指標ID
extname
name
延伸功能名稱
extowner
oid
``pg_authid.oid
延伸功能的擁有者
extnamespace
oid
``pg_namespace.oid
延伸功能之中所導出物件的綱要名稱
extrelocatable
bool
如果延伸功能可以接受重新定位到另一個綱要之中，則為 True
extversion
text
延伸功能的版本名稱
extconfig
oid[]
``pg_class.oid
延伸功能組態資料表的 regclass OID 陣列，如果沒有，則為 NULL
extcondition
text[]
延伸功能組態資料表的 WHERE 子句過濾條件陣列，如果沒有，則為 NULL
stanumbersN float4[]
Numerical statistics of the appropriate kind for the Nth “slot”, or null if the slot kind does not involve numerical values
stavaluesN anyarray
Column data values of the appropriate kind for the Nth “slot”, or null if the slot kind does not store any data values. Each array's element values are actually of the specific column's data type, or a related type such as an array's element type, so there is no way to define these columns' type more specifically than anyarray.
rolconnlimit int4
For roles that can log in, this sets maximum number of concurrent connections this role can make. -1 means no limit.
rolpassword text
Password (possibly encrypted); null if none. The format depends on the form of encryption used.
rolvaliduntil timestamptz
Password expiry time (only used for password authentication); null if no expiration
lanpltrusted
bool
如果這是一種受信任的語言，則為 True，這意味著它被認為不會授予對正常 SQL 執行環境之外任何內容的存取權限。只有超級使用者才能以不受信任的語言建立函數。
lanplcallfoid
oid
``.oid
對於非內部語言，這引用了語言處理程序，它是一個特殊的函數，負責執行使用特定語言所編寫的所有函數。
laninline
oid
``.oid
這引用了一個負責執行 “inline” 匿名程式區塊（ 區塊）的函數。如果不支援 inline 區塊，則為零。
lanvalidator
oid
``.oid
這引用了一個語言驗證器函數，該函數負責在建立新函數時檢查它們的語法和有效性。如果未提供驗證器，則為零。
lanacl
aclitem[]
存取權限；有關詳細訊息，請參閱 和
oid
oid
資料列識別指標（隱藏屬性；必須明確選擇）
lanname
name
語言名稱
lanowner
oid
``pg_authid.oid
語言的所有者
lanispl
bool
對於內部語言（例如 SQL）而言這是 false 的，對於使用者定義的語言則是 true。目前，pg_dump 仍然使用它來決定需要轉存哪些語言，但將來可能會被不同的機制所取代。
indexrelid oid (references .oid)
The OID of the pg_class entry for this index
indrelid oid (references .oid)
The OID of the pg_class entry for the table this index is for
indnatts int2
The total number of columns in the index (duplicates pg_class.relnatts); this number includes both key and included attributes
indnkeyatts int2
The number of key columns in the index, not counting any included columns, which are merely stored and do not participate in the index semantics
indisunique bool
If true, this is a unique index
indisprimary bool
If true, this index represents the primary key of the table (indisunique should always be true when this is true)
indisexclusion bool
If true, this index supports an exclusion constraint
indimmediate bool
If true, the uniqueness check is enforced immediately on insertion (irrelevant if indisunique is not true)
indisclustered bool
If true, the table was last clustered on this index
indisvalid bool
If true, the index is currently valid for queries. False means the index is possibly incomplete: it must still be modified by INSERT/UPDATE operations, but it cannot safely be used for queries. If it is unique, the uniqueness property is not guaranteed true either.
indcheckxmin bool
If true, queries must not use the index until the xmin of this pg_index row is below their TransactionXmin event horizon, because the table may contain broken HOT chains with incompatible rows that they can see
indisready bool
If true, the index is currently ready for inserts. False means the index must be ignored by INSERT/UPDATE operations.
indislive bool
If false, the index is in process of being dropped, and should be ignored for all purposes (including HOT-safety decisions)
indisreplident bool
If true this index has been chosen as “replica identity” using ALTER TABLE ... REPLICA IDENTITY USING INDEX ...
indkey int2vector (references .attnum)
This is an array of indnatts values that indicate which table columns this index indexes. For example a value of 1 3 would mean that the first and the third table columns make up the index entries. Key columns come before non-key (included) columns. A zero in this array indicates that the corresponding index attribute is an expression over the table columns, rather than a simple column reference.
indcollation oidvector (references .oid)
For each column in the index key (indnkeyatts values), this contains the OID of the collation to use for the index, or zero if the column is not of a collatable data type.
indclass oidvector (references .oid)
For each column in the index key (indnkeyatts values), this contains the OID of the operator class to use. See for details.
indoption int2vector
This is an array of indnkeyatts values that store per-column flag bits. The meaning of the bits is defined by the index's access method.
indexprs pg_node_tree
Expression trees (in nodeToString() representation) for index attributes that are not simple column references. This is a list with one element for each zero entry in indkey. Null if all index attributes are simple references.
indpred pg_node_tree
Expression tree (in nodeToString() representation) for partial index predicate. Null if not a partial index.
Column Type
Description
The catalog pg_trigger stores triggers on tables and views. See for more information.
Table 51.56. pg_trigger Columns
The view pg_locks provides access to information about the locks held by active processes within the database server. See for more discussion of locking.
pg_locks contains one row per active lockable object, requested lock mode, and relevant process. Thus, the same lockable object might appear many times, if multiple processes are holding or waiting for locks on it. However, an object that currently has no locks on it will not appear at all.
There are several distinct types of lockable objects: whole relations (e.g., tables), individual pages of relations, individual tuples of relations, transaction IDs (both virtual and permanent IDs), and general database objects (identified by class OID and object OID, in the same way as in pg_description or pg_depend). Also, the right to extend a relation is represented as a separate lockable object, as is the right to update pg_database.datfrozenxid
Row identifier (hidden attribute; must be explicitly selected)
tgrelid
oid
.oid
The table this trigger is on
tgname
name
Trigger name (must be unique among triggers of same table)
tgfoid
oid
.oid
The function to be called
tgtype
int2
Bit mask identifying trigger firing conditions
tgenabled
char
Controls in which modes the trigger fires. O = trigger fires in “origin” and “local” modes, D = trigger is disabled, R = trigger fires in “replica” mode, A = trigger fires always.
tgisinternal
bool
True if trigger is internally generated (usually, to enforce the constraint identified by tgconstraint)
tgconstrrelid
oid
.oid
The table referenced by a referential integrity constraint
tgconstrindid
oid
.oid
The index supporting a unique, primary key, referential integrity, or exclusion constraint
tgconstraint
oid
.oid
The pg_constraint entry associated with the trigger, if any
tgdeferrable
bool
True if constraint trigger is deferrable
tginitdeferred
bool
True if constraint trigger is initially deferred
tgnargs
int2
Number of argument strings passed to trigger function
tgattr
int2vector
.attnum
Column numbers, if trigger is column-specific; otherwise an empty array
tgargs
bytea
Argument strings to pass to trigger, each NULL-terminated
tgqual
pg_node_tree
Expression tree (in nodeToString() representation) for the trigger's WHEN condition, or null if none
tgoldtable
name
REFERENCING clause name for OLD TABLE, or null if none
tgnewtable
name
REFERENCING clause name for NEW TABLE, or null if none
Currently, column-specific triggering is supported only for UPDATE events, and so tgattr is relevant only for that event type. tgtype might contain bits for other event types as well, but those are presumed to be table-wide regardless of what is in tgattr.
When tgconstraint is nonzero, tgconstrrelid, tgconstrindid, tgdeferrable, and tginitdeferred are largely redundant with the referenced pg_constraint entry. However, it is possible for a non-deferrable trigger to be associated with a deferrable constraint: foreign key constraints can have some deferrable and some non-deferrable triggers.
pg_class.relhastriggers must be true if a relation has any triggers in this catalog.
oid
oid
Column Type
Description
locktype text
Type of the lockable object: relation, extend, frozenid, page, tuple, transactionid, virtualxid, spectoken, object, userlock, or
database oid (references .oid)
OID of the database in which the lock target exists, or zero if the target is a shared object, or null if the target is a transaction ID
relation oid (references .oid)
OID of the relation targeted by the lock, or null if the target is not a relation or part of a relation
page int4
Page number targeted by the lock within the relation, or null if the target is not a relation page or tuple
tuple int2
Tuple number targeted by the lock within the page, or null if the target is not a tuple
virtualxid text
Virtual ID of the transaction targeted by the lock, or null if the target is not a virtual transaction ID
transactionid xid
ID of the transaction targeted by the lock, or null if the target is not a transaction ID
classid oid (references .oid)
OID of the system catalog containing the lock target, or null if the target is not a general database object
objid oid (references any OID column)
OID of the lock target within its system catalog, or null if the target is not a general database object
granted 為 true 的話，代表此鎖定由該筆資料的程序所持有。False 表示此程序目前正在等待取得鎖定，這意味著至少一個其他程序正持有或等待同一可鎖定物件上在鎖定模式有衝突。等待的程序將會一直休眠，直到另一個鎖定被釋放（或檢測到 deadlock 情況）為止。一個程序等待最多只可以取得一個鎖定。
在整個交易事務執行過程中，伺服器程序對事務的虛擬事務 ID 持有排他鎖定(exclusive lock)。如果將永久性 ID 分配給事務（通常僅在事務變更資料庫狀態時才會發生），它還會對事務的永久性事務 ID 持有排他鎖定，直到結束。當一個程序發現有必要專門等待另一個事務結束時，它透過嘗試獲取另一個事務的 ID（取決於情況的虛擬 ID 或永久 ID）上的共享鎖定(share lock)來做到這一點。僅當另一個事務結束並釋放其鎖定時，該操作才會成功。
儘管 tuple 是可鎖定的物件型別，但是有關資料列級鎖定的資訊是儲存在磁碟上，而不是儲存在記憶體之中，因此資料列級的鎖定通常不會出現在此檢視表中。如果程序正在等待資料列級的鎖定，則它通常在檢視表中顯示為正在等待該資料列鎖定目前持有者的永久事務 ID。
Advisory locks can be acquired on keys consisting of either a single bigint value or two integer values. A bigint key is displayed with its high-order half in the classid column, its low-order half in the objid column, and objsubid equal to 1. The original bigint value can be reassembled with the expression (classid::bigint << 32) | objid::bigint. Integer keys are displayed with the first key in the classid column, the second key in the objid column, and objsubid equal to 2. The actual meaning of the keys is up to the user. Advisory locks are local to each database, so the database column is meaningful for an advisory lock.
pg_locks provides a global view of all locks in the database cluster, not only those relevant to the current database. Although its relation column can be joined against pg_class.oid to identify locked relations, this will only work correctly for relations in the current database (those for which the database column is either the current database's OID or zero).
The pid column can be joined to the pid column of the pg_stat_activity view to get more information on the session holding or awaiting each lock, for example
Also, if you are using prepared transactions, the virtualtransaction column can be joined to the transaction column of the pg_prepared_xacts view to get more information on prepared transactions that hold locks. (A prepared transaction can never be waiting for a lock, but it continues to hold the locks it acquired while running.) For example:
While it is possible to obtain information about which processes block which other processes by joining pg_locks against itself, this is very difficult to get right in detail. Such a query would have to encode knowledge about which lock modes conflict with which others. Worse, the pg_locks view does not expose information about which processes are ahead of which others in lock wait queues, nor information about which processes are parallel workers running on behalf of which other client sessions. It is better to use the pg_blocking_pids() function (see Table 9.63) to identify which process(es) a waiting process is blocked behind.
The pg_locks view displays data from both the regular lock manager and the predicate lock manager, which are separate systems; in addition, the regular lock manager subdivides its locks into regular and fast-path locks. This data is not guaranteed to be entirely consistent. When the view is queried, data on fast-path locks (with fastpath = true) is gathered from each backend one at a time, without freezing the state of the entire lock manager, so it is possible for locks to be taken or released while information is gathered. Note, however, that these locks are known not to conflict with any other lock currently in place. After all backends have been queried for fast-path locks, the remainder of the regular lock manager is locked as a unit, and a consistent snapshot of all remaining locks is collected as an atomic action. After unlocking the regular lock manager, the predicate lock manager is similarly locked and all predicate locks are collected as an atomic action. Thus, with the exception of fast-path locks, each lock manager will deliver a consistent set of results, but as we do not lock both lock managers simultaneously, it is possible for locks to be taken or released after we interrogate the regular lock manager and before we interrogate the predicate lock manager.
Locking the regular and/or predicate lock manager could have some impact on database performance if this view is very frequently accessed. The locks are held only for the minimum amount of time necessary to obtain data from the lock managers, but this does not completely eliminate the possibility of a performance impact.\
版本：11
The catalog pg_class catalogs tables and most everything else that has columns or is otherwise similar to a table. This includes indexes (but see also pg_index), sequences (but see also pg_sequence), views, materialized views, composite types, and TOAST tables; see relkind. Below, when we mean all of these kinds of objects we speak of “relations”. Not all columns are meaningful for all relation types.
pg_class ColumnsSeveral of the Boolean flags in pg_class are maintained lazily: they are guaranteed to be true if that's the correct state, but may not be reset to false immediately when the condition is no longer true. For example, relhasindex is set by CREATE INDEX, but it is never cleared by DROP INDEX. Instead, VACUUM clears relhasindex if it finds the table has no indexes. This arrangement avoids race conditions and improves concurrency.\
SELECT * FROM pg_locks pl LEFT JOIN pg_stat_activity psa
ON pl.pid = psa.pid;SELECT * FROM pg_locks pl LEFT JOIN pg_prepared_xacts ppx
ON pl.virtualtransaction = '-1/' || ppx.transaction;advisoryobjsubid int2
Column number targeted by the lock (the classid and objid refer to the table itself), or zero if the target is some other general database object, or null if the target is not a general database object
virtualtransaction text
Virtual ID of the transaction that is holding or awaiting this lock
pid int4
Process ID of the server process holding or awaiting this lock, or null if the lock is held by a prepared transaction
mode text
Name of the lock mode held or desired by this process (see Section 13.3.1 and Section 13.2.3)
granted bool
True if lock is held, false if lock is awaited
fastpath bool
True if lock was taken via fast path, false if taken via main lock table
reltuples float4
Number of live rows in the table. This is only an estimate used by the planner. It is updated by VACUUM, ANALYZE, and a few DDL commands such as CREATE INDEX.
relallvisible int4
Number of pages that are marked all-visible in the table's visibility map. This is only an estimate used by the planner. It is updated by VACUUM, ANALYZE, and a few DDL commands such as CREATE INDEX.
reltoastrelid oid (references .oid)
OID of the TOAST table associated with this table, 0 if none. The TOAST table stores large attributes “out of line” in a secondary table.
relhasindex bool
True if this is a table and it has (or recently had) any indexes
relisshared bool
True if this table is shared across all databases in the cluster. Only certain system catalogs (such as pg_database) are shared.
relpersistence char
p = permanent table, u = unlogged table, t = temporary table
relkind char
r = ordinary table, i = index, S = sequence, t = TOAST table, v = view, m = materialized view, c = composite type, f = foreign table, p = partitioned table, I = partitioned index
relnatts int2
Number of user columns in the relation (system columns not counted). There must be this many corresponding entries in pg_attribute. See also pg_attribute.attnum.
relchecks int2
Number of CHECK constraints on the table; see catalog
relhasrules bool
True if table has (or once had) rules; see catalog
relhastriggers bool
True if table has (or once had) triggers; see catalog
relhassubclass bool
True if table or index has (or once had) any inheritance children
relrowsecurity bool
True if table has row level security enabled; see catalog
relforcerowsecurity bool
True if row level security (when enabled) will also apply to table owner; see catalog
relispopulated bool
True if relation is populated (this is true for all relations other than some materialized views)
relreplident char
Columns used to form “replica identity” for rows: d = default (primary key, if any), n = nothing, f = all columns, i = index with indisreplident set (same as nothing if the index used has been dropped)
relispartition bool
True if table or index is a partition
relrewrite oid (references .oid)
For new relations being written during a DDL operation that requires a table rewrite, this contains the OID of the original relation; otherwise 0. That state is only visible internally; this field should never contain anything other than 0 for a user-visible relation.
relfrozenxid xid
All transaction IDs before this one have been replaced with a permanent (“frozen”) transaction ID in this table. This is used to track whether the table needs to be vacuumed in order to prevent transaction ID wraparound or to allow pg_xact to be shrunk. Zero (InvalidTransactionId) if the relation is not a table.
relminmxid xid
All multixact IDs before this one have been replaced by a transaction ID in this table. This is used to track whether the table needs to be vacuumed in order to prevent multixact ID wraparound or to allow pg_multixact to be shrunk. Zero (InvalidMultiXactId) if the relation is not a table.
relacl aclitem[]
Access privileges; see for details
reloptions text[]
Access-method-specific options, as “keyword=value” strings
relpartbound pg_node_tree
If table is a partition (see relispartition), internal representation of the partition bound
Column Type
Description
oid oid
Row identifier
relname name
Name of the table, index, view, etc.
relnamespace oid (references pg_namespace.oid)
The OID of the namespace that contains this relation
reltype oid (references pg_type.oid)
The OID of the data type that corresponds to this table's row type, if any (zero for indexes, which have no pg_type entry)
reloftype oid (references pg_type.oid)
For typed tables, the OID of the underlying composite type, zero for all other relations
relowner oid (references pg_authid.oid)
Owner of the relation
relam oid (references pg_am.oid)
If this is a table or an index, the access method used (heap, B-tree, hash, etc.)
relfilenode oid
Name of the on-disk file of this relation; zero means this is a “mapped” relation whose disk file name is determined by low-level state
reltablespace oid (references pg_tablespace.oid)
The tablespace in which this relation is stored. If zero, the database's default tablespace is implied. (Not meaningful if the relation has no on-disk file.)
relpages int4
Size of the on-disk representation of this table in pages (of size BLCKSZ). This is only an estimate used by the planner. It is updated by VACUUM, ANALYZE, and a few DDL commands such as CREATE INDEX.
The catalog pg_constraint stores check, primary key, unique, foreign key, and exclusion constraints on tables. (Column constraints are not treated specially. Every column constraint is equivalent to some table constraint.) Not-null constraints are represented in the pg_attribute catalog, not here.
User-defined constraint triggers (created with CREATE CONSTRAINT TRIGGER) also give rise to an entry in this table.
Check constraints on domains are stored here, too.
Table 51.13. pg_constraint Columns
In the case of an exclusion constraint, conkey is only useful for constraint elements that are simple column references. For other cases, a zero appears in conkey and the associated index must be consulted to discover the expression that is constrained. (conkey thus has the same contents as pg_index.indkey for the index.)
consrc is not updated when referenced objects change; for example, it won't track renaming of columns. Rather than relying on this field, it's best to use pg_get_constraintdef() to extract the definition of a check constraint.
pg_class.relchecks needs to agree with the number of check-constraint entries found in this table for each relation.
condeferrable
bool
Is the constraint deferrable?
condeferred
bool
Is the constraint deferred by default?
convalidated
bool
Has the constraint been validated? Currently, can only be false for foreign keys and CHECK constraints
conrelid
oid
.oid
The table this constraint is on; 0 if not a table constraint
contypid
oid
.oid
The domain this constraint is on; 0 if not a domain constraint
conindid
oid
.oid
The index supporting this constraint, if it's a unique, primary key, foreign key, or exclusion constraint; else 0
confrelid
oid
.oid
If a foreign key, the referenced table; else 0
confupdtype
char
Foreign key update action code: a = no action, r = restrict, c = cascade, n = set null, d = set default
confdeltype
char
Foreign key deletion action code: a = no action, r = restrict, c = cascade, n = set null, d = set default
confmatchtype
char
Foreign key match type: f = full, p = partial, s = simple
conislocal
bool
This constraint is defined locally for the relation. Note that a constraint can be locally defined and inherited simultaneously.
coninhcount
int4
The number of direct inheritance ancestors this constraint has. A constraint with a nonzero number of ancestors cannot be dropped nor renamed.
connoinherit
bool
This constraint is defined locally for the relation. It is a non-inheritable constraint.
conkey
int2[]
.attnum
If a table constraint (including foreign keys, but not constraint triggers), list of the constrained columns
confkey
int2[]
.attnum
If a foreign key, list of the referenced columns
conpfeqop
oid[]
.oid
If a foreign key, list of the equality operators for PK = FK comparisons
conppeqop
oid[]
.oid
If a foreign key, list of the equality operators for PK = PK comparisons
conffeqop
oid[]
.oid
If a foreign key, list of the equality operators for FK = FK comparisons
conexclop
oid[]
.oid
If an exclusion constraint, list of the per-column exclusion operators
conbin
pg_node_tree
If a check constraint, an internal representation of the expression
consrc
text
If a check constraint, a human-readable representation of the expression
oid
oid
Row identifier (hidden attribute; must be explicitly selected)
conname
name
Constraint name (not necessarily unique!)
connamespace
oid
pg_namespace.oid
The OID of the namespace that contains this constraint
contype
char
c = check constraint, f = foreign key constraint, p = primary key constraint, u = unique constraint, t = constraint trigger, x = exclusion constraint
版本：11
目錄 pg_proc 儲存有關函數、程序函數、彙總函數和窗函數（或統稱為 routines）的資訊。 有關更多資訊，請參閱 CREATE FUNCTION，CREATE PROCEDURE 和第 37.3 節。
如果 prokind 指示該項目用於彙總函數，則 pg_aggregate 中應有相對應的資料列。
pg_proc Columns對於內建和動態載入的已編譯函數，prosrc 包含函數的 C 語言名稱（link symbol）。 對於所有其他目前已知的語言類型，prosrc 包含函數的原始碼。除了動態載入的 C 函數外，probin 均未使用，因為它用於記錄該函數的共享函式庫檔案的名稱。
prolang
oid
.oid
Implementation language or call interface of this function
procost
float4
Estimated execution cost (in units of ); if proretset, this is cost per row returned
prorows
float4
Estimated number of result rows (zero if not proretset)
provariadic
oid
.oid
Data type of the variadic array parameter's elements, or zero if the function does not have a variadic parameter
protransform
regproc
.oid
Calls to this function can be simplified by this other function (see )
prokind
char
f for a normal function, p for a procedure, a for an aggregate function, or w for a window function
prosecdef
bool
Function is a security definer (i.e., a “setuid” function)
proleakproof
bool
The function has no side effects. No information about the arguments is conveyed except via the return value. Any function that might throw an error depending on the values of its arguments is not leak-proof.
proisstrict
bool
Function returns null if any call argument is null. In that case the function won't actually be called at all. Functions that are not “strict” must be prepared to handle null inputs.
proretset
bool
Function returns a set (i.e., multiple values of the specified data type)
provolatile
char
provolatile tells whether the function's result depends only on its input arguments, or is affected by outside factors. It is i for “immutable” functions, which always deliver the same result for the same inputs. It is s for “stable” functions, whose results (for fixed inputs) do not change within a scan. It is v for “volatile” functions, whose results might change at any time. (Use v also for functions with side-effects, so that calls to them cannot get optimized away.)
proparallel
char
proparallel tells whether the function can be safely run in parallel mode. It is s for functions which are safe to run in parallel mode without restriction. It is r for functions which can be run in parallel mode, but their execution is restricted to the parallel group leader; parallel worker processes cannot invoke these functions. It is u for functions which are unsafe in parallel mode; the presence of such a function forces a serial execution plan.
pronargs
int2
Number of input arguments
pronargdefaults
int2
Number of arguments that have defaults
prorettype
oid
.oid
Data type of the return value
proargtypes
oidvector
.oid
An array with the data types of the function arguments. This includes only input arguments (including INOUT and VARIADIC arguments), and thus represents the call signature of the function.
proallargtypes
oid[]
.oid
An array with the data types of the function arguments. This includes all arguments (including OUT and INOUT arguments); however, if all the arguments are IN arguments, this field will be null. Note that subscripting is 1-based, whereas for historical reasons proargtypes is subscripted from 0.
proargmodes
char[]
An array with the modes of the function arguments, encoded as i for IN arguments, o for OUT arguments, b for INOUT arguments, v for VARIADIC arguments, t for TABLE arguments. If all the arguments are IN arguments, this field will be null. Note that subscripts correspond to positions of proallargtypes not proargtypes
proargnames
text[]
An array with the names of the function arguments. Arguments without a name are set to empty strings in the array. If none of the arguments have a name, this field will be null. Note that subscripts correspond to positions of proallargtypes not proargtypes.
proargdefaults
pg_node_tree
Expression trees (in nodeToString() representation) for default values. This is a list with pronargdefaults elements, corresponding to the last N input arguments (i.e., the last N proargtypes positions). If none of the arguments have defaults, this field will be null.
protrftypes
oid[]
Data type OIDs for which to apply transforms.
prosrc
text
This tells the function handler how to invoke the function. It might be the actual source code of the function for interpreted languages, a link symbol, a file name, or just about anything else, depending on the implementation language/call convention.
probin
text
Additional information about how to invoke the function. Again, the interpretation is language-specific.
proconfig
text[]
Function's local settings for run-time configuration variables
proacl
aclitem[]
Access privileges; see and for details
oid
oid
Row identifier (hidden attribute; must be explicitly selected)
proname
name
Name of the function
pronamespace
oid
pg_namespace.oid
The OID of the namespace that contains this function
proowner
oid
pg_authid.oid
Owner of the function
Column Type
Description
oid oid
Row identifier
nspname name
Name of the namespace
nspowner oid (references pg_authid.oid)
Owner of the namespace
nspacl aclitem[]
存取權限； 詳見 5.7 節
The catalog pg_type stores information about data types. Base types and enum types (scalar types) are created with CREATE TYPE, and domains with CREATE DOMAIN. A composite type is automatically created for each table in the database, to represent the row structure of the table. It is also possible to create composite types with CREATE TYPE AS.
Table 51.62. pg_type Columns
lists the system-defined values of typcategory. Any future additions to this list will also be upper-case ASCII letters. All other ASCII characters are reserved for user-defined categories.
Table 51.63. typcategory Codes
Geometric types
I
Network address types
N
Numeric types
P
Pseudo-types
R
Range types
S
String types
T
Timespan types
U
User-defined types
V
Bit-string types
X
unknown type
oid
oid
Row identifier (hidden attribute; must be explicitly selected)
typname
name
Data type name
typnamespace
oid
pg_namespace.oid
The OID of the namespace that contains this type
typowner
oid
pg_authid.oid
Owner of the type
typlen
int2
For a fixed-size type, typlen is the number of bytes in the internal representation of the type. But for a variable-length type, typlenis negative. -1 indicates a “varlena” type (one that has a length word), -2 indicates a null-terminated C string.
typbyval
bool
typbyval determines whether internal routines pass a value of this type by value or by reference. typbyval had better be false if typlen is not 1, 2, or 4 (or 8 on machines where Datum is 8 bytes). Variable-length types are always passed by reference. Note that typbyval can be false even if the length would allow pass-by-value.
typtype
char
typtype is b for a base type, c for a composite type (e.g., a table's row type), d for a domain, e for an enum type, p for a pseudo-type, or r for a range type. See also typrelid and typbasetype.
typcategory
char
typcategory is an arbitrary classification of data types that is used by the parser to determine which implicit casts should be “preferred”. See Table 51.63.
typispreferred
bool
True if the type is a preferred cast target within its typcategory
typisdefined
bool
True if the type is defined, false if this is a placeholder entry for a not-yet-defined type. When typisdefined is false, nothing except the type name, namespace, and OID can be relied on.
typdelim
char
Character that separates two values of this type when parsing array input. Note that the delimiter is associated with the array element data type, not the array data type.
typrelid
oid
pg_class.oid
If this is a composite type (see typtype), then this column points to the pg_class entry that defines the corresponding table. (For a free-standing composite type, the pg_class entry doesn't really represent a table, but it is needed anyway for the type'spg_attribute entries to link to.) Zero for non-composite types.
typelem
oid
pg_type.oid
If typelem is not 0 then it identifies another row in pg_type. The current type can then be subscripted like an array yielding values of type typelem. A “true” array type is variable length (typlen = -1), but some fixed-length (typlen > 0) types also have nonzero typelem, for example name and point. If a fixed-length type has a typelem then its internal representation must be some number of values of the typelem data type with no other data. Variable-length array types have a header defined by the array subroutines.
typarray
oid
pg_type.oid
If typarray is not 0 then it identifies another row in pg_type, which is the “true” array type having this type as element
typinput
regproc
pg_proc.oid
Input conversion function (text format)
typoutput
regproc
pg_proc.oid
Output conversion function (text format)
typreceive
regproc
pg_proc.oid
Input conversion function (binary format), or 0 if none
typsend
regproc
pg_proc.oid
Output conversion function (binary format), or 0 if none
typmodin
regproc
pg_proc.oid
Type modifier input function, or 0 if type does not support modifiers
typmodout
regproc
pg_proc.oid
Type modifier output function, or 0 to use the standard format
typanalyze
regproc
pg_proc.oid
Custom ANALYZE function, or 0 to use the standard function
typalign
char
typalign is the alignment required when storing a value of this type. It applies to storage on disk as well as most representations of the value inside PostgreSQL. When multiple values are stored consecutively, such as in the representation of a complete row on disk, padding is inserted before a datum of this type so that it begins on the specified boundary. The alignment reference is the beginning of the first datum in the sequence.Possible values are:c = char alignment, i.e., no alignment needed.s = short alignment (2 bytes on most machines).i = int alignment (4 bytes on most machines).d = double alignment (8 bytes on many machines, but by no means all).NoteFor types used in system tables, it is critical that the size and alignment defined in pg_typeagree with the way that the compiler will lay out the column in a structure representing a table row.
typstorage
char
typstorage tells for varlena types (those with typlen = -1) if the type is prepared for toasting and what the default strategy for attributes of this type should be. Possible values arep: Value must always be stored plain.e: Value can be stored in a “secondary” relation (if relation has one, see pg_class.reltoastrelid).m: Value can be stored compressed inline.x: Value can be stored compressed inline or stored in “secondary” storage.Note that m columns can also be moved out to secondary storage, but only as a last resort (e and x columns are moved first).
typnotnull
bool
typnotnull represents a not-null constraint on a type. Used for domains only.
typbasetype
oid
pg_type.oid
If this is a domain (see typtype), then typbasetype identifies the type that this one is based on. Zero if this type is not a domain.
typtypmod
int4
Domains use typtypmod to record the typmod to be applied to their base type (-1 if base type does not use a typmod). -1 if this type is not a domain.
typndims
int4
typndims is the number of array dimensions for a domain over an array (that is, typbasetype is an array type). Zero for types other than domains over array types.
typcollation
oid
pg_collation.oid
typcollation specifies the collation of the type. If the type does not support collations, this will be zero. A base type that supports collations will have DEFAULT_COLLATION_OID here. A domain over a collatable type can have some other collation OID, if one was specified for the domain.
typdefaultbin
pg_node_tree
If typdefaultbin is not null, it is the nodeToString() representation of a default expression for the type. This is only used for domains.
typdefault
text
typdefault is null if the type has no associated default value. If typdefaultbin is not null, typdefault must contain a human-readable version of the default expression represented by typdefaultbin. If typdefaultbin is null and typdefault is not, then typdefault is the external representation of the type's default value, which can be fed to the type's input converter to produce a constant.
typacl
aclitem[]
A
Array types
B
Boolean types
C
Composite types
D
Date/time types
E
Enum types
G