{"kind": "type", "slug": "fdw_handler", "name": "fdw_handler", "major": "18", "snapshot": {"casts": [], "facts": [{"label": "Catalog name", "value": "pg_catalog.fdw_handler"}, {"label": "Type OID", "value": "3115"}, {"label": "Type kind", "value": "Pseudo-type"}, {"label": "Declared length", "value": "4 bytes"}, {"label": "Storage strategy", "value": "plain"}, {"label": "Input function", "value": "fdw_handler_in"}, {"label": "Output function", "value": "fdw_handler_out"}, {"label": "Documented declaration", "value": "fdw_handler"}, {"label": "Manual description", "value": "A foreign-data wrapper handler is declared to return fdw_handler ."}], "ranges": [], "aliases": [], "catalog": {"oid": "3115", "descr": "pseudo-type for the result of an FDW handler function", "typacl": "_null_", "typlen": "4", "typelem": "0", "typname": "fdw_handler", "typsend": "-", "typtype": "p", "typalign": "i", "typarray": "0", "typbyval": "t", "typdelim": "','", "typinput": "fdw_handler_in", "typmodin": "-", "typndims": "0", "typowner": "POSTGRES", "typrelid": "0", "typmodout": "-", "typoutput": "fdw_handler_out", "typtypmod": "-1", "typanalyze": "-", "typdefault": "_null_", "typnotnull": "f", "typreceive": "-", "typstorage": "p", "typbasetype": "0", "typcategory": "P", "typcollation": "0", "typisdefined": "t", "typnamespace": "pg_catalog", "typsubscript": "-", "typdefaultbin": "_null_", "array_type_oid": "0", "typispreferred": "f", "array_type_name": ""}, "related": [{"url": "/wiki/catalog/pg_type/?v=18", "label": "pg_type catalog"}, {"url": "/wiki/catalog/pg_cast/?v=18", "label": "pg_cast catalog"}, {"url": "/wiki/catalog/pg_operator/?v=18", "label": "pg_operator catalog"}, {"url": "/wiki/catalog/pg_opclass/?v=18", "label": "pg_opclass catalog"}, {"url": "/wiki/type/arrays/?v=18", "label": "Arrays"}], "release": {"ref": "https://ftp.postgresql.org/pub/source/v18.6/postgresql-18.6.tar.bz2", "label": "18.6", "major": "18", "channel": "stable", "revision": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f", "source_files": {"doc/src/sgml/datatype.sgml": "86328daa77e20d81d222376ec0306d9841a17104e436c08d138eb763aefb3700", "src/include/catalog/pg_am.h": "3426799df799f32163fcc0765f43dbdb5e88e626acf31284fef9fc6014b69d8e", "src/include/catalog/pg_am.dat": "b3cb86b102a42fb0024cbd99779c9897afb40d12a71f5cc5a0e5aee7ff2f9969", "src/include/catalog/pg_cast.h": "de585c7df687d698e7d1d100dce8a794ac9da52414ea48169191019178c8f053", "src/include/catalog/pg_proc.h": "f7d59f07c5b95e2f3c7141762a0f576e8a3af7581ba54c27537f4d500472bea5", "src/include/catalog/pg_type.h": "8fb198749fd82b6c1818a3c18455f226f66116fcfeb3d4959c65ce3fda22802e", "src/include/catalog/pg_range.h": "45546d952b5181f989bd9234721897fc2b37005c8e49ce2ddc156f26974c3ca4", "src/include/catalog/pg_cast.dat": "97911281ca2c81917394ccb2ec13367e37c6801fd461d5e1a3d2f28b911b46b2", "src/include/catalog/pg_proc.dat": "1f934ce80d460159dda137714374a35f9896315ea2476709cbb4da13b38ef95a", "src/include/catalog/pg_type.dat": "5f5887b75677cba2d4a1a0cfeb355df5ed91f85d385fac88bd8d7c605b3578f9", "src/include/catalog/pg_opclass.h": "9c218537806c8ef0398302faaca7f91315dfc1198c48706cebffb479b68defaf", "src/include/catalog/pg_range.dat": "5c2271f8e89e9378d1887204e5785060b77405b5f0ff3e6c719250c9c1dcfcc4", "src/include/catalog/pg_operator.h": "621b18cfffe102413d79b746ce7a10f77fc60fdd097bac34c22b31070d3ee3c4", "src/include/catalog/pg_opfamily.h": "e1f5fc8aebd3042df847455bf66bf755f768c2aa8a9b03d22f7ec8563eba59c0", "src/include/catalog/pg_opclass.dat": "4ee7d3619a6aa106e1c0db55de903931c7d11b1c60ba053a022519c55f8ee668", "src/include/catalog/pg_operator.dat": "5d35b9b2ef5f9797cc815263927ef8a12367fedace53e828b4e8b320e2a7f703", "src/include/catalog/pg_opfamily.dat": "3b694879027b858f2ecf1fa1152b7e30c6e15a216ba99c2384291c30e9d52311"}, "manual_sha256": {"arrays.html": "0e1d5c5a7b4a949d4439995f44f74ad4264e050d16eb9ad2a850fbaee04032df", "domains.html": "82d486973ccc35d14276627a67ac76b434452f23f9ed4d8aa3fbb01fdf285fc2", "datatype.html": "e581f67c74e42006289638c8659e9b338adbfd7f068bd8bf2b3be3880fcd2254", "rowtypes.html": "74f99e029c3a9edfd3e18810ba3c8cb66d3aada91eb67b86476560871e6617e9", "rangetypes.html": "e4960abc7ce8e51d794f94f1e57b099d30b7f75dd7f2b23a960eef91f6291c33", "datatype-bit.html": "c49124aad561636c18080b9e09572fde7785a6b9eae86f5a33283f0fd6774c37", "datatype-oid.html": "8b3360302225f08ae72716ce1804596de95b568e5d31f788cb4597427b28cc38", "datatype-xml.html": "061fc2295b7b69be704f0a741b8decd10ad721059f871fb0243c669bb54d7822", "datatype-enum.html": "cab38e53222e30cc94b24de4b33634fd22d7c93f58ebcf35f646c9b8da78fae8", "datatype-json.html": "650162a05b660146b500a205d523374d00aee117a6a6240d30262be51b6e33e5", "datatype-uuid.html": "292b307b3223c6182bdba687e7f69e6dca9038430143ad79d56327f6ed4c3246", "datatype-money.html": "8b29c14b90679683ac5c472b59a0a7e2853f32cc7db43fab417b2697a6879964", "functions-info.html": "78ac80bf81da2e4f4a33f3b850faa86f0f58ec54a083d6c31da557907de0df87", "catalog-pg-type.html": "ea9c9313bab8e92a7da18ebc50c7ff1f908dd80999a7e0ca3bbc82ba626c58d4", "datatype-binary.html": "0c03ec47b76e37888a3da7f5dcfd340128a5d356642a85185cc9ebe17856a904", "datatype-pg-lsn.html": "339172f5107cc7eb7139bec911277647219e92a532cebd0f3da0a5dacf8195af", "datatype-pseudo.html": "c7cf0b8214304bd8702c95f2142671ae5f0d631f83717f9c07d9e1f2579961b4", "datatype-boolean.html": "b633f663e6c8276e7056287640c413aa79dbc15d5353cee0d41653d58d376956", "datatype-numeric.html": "b74619f7ac2f1ca9f85c48073df78c33dd30e464e61baba6008634534edcb500", "sql-createdomain.html": "e94f927196de1b0ea1ce35cd4603c1f6f544439adcc0edf1c4222358e832245b", "datatype-datetime.html": "e366275d8b13845bfa4ef0d68faa093e5f3ecb708a1ec870cbcbf7e425b85699", "datatype-character.html": "c73eebe413ea709a7792e4cfc3cfe9fb68cb496ebe83c3ebaa9d09f8c40d0f73", "datatype-geometric.html": "0eb3053cfe7d6b0a4b5592c5d7af8d97cae527e87f063c5793413bcba5c14cd9", "datatype-net-types.html": "96846e641cc37727ddcd8b8a1aa0dbe33cd9787760a2b4efb0dcb9403d5be63f", "datatype-textsearch.html": "4b15e05be8b49a71b28aea22f2c46d0dbf639a91e7b4fe129a4c737c6daad47c"}, "source_sha256": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}, "sources": [{"url": "/docs/18/datatype-pseudo.html", "path": "datatype-pseudo.html", "label": "PostgreSQL 18 English manual", "sha256": "c7cf0b8214304bd8702c95f2142671ae5f0d631f83717f9c07d9e1f2579961b4"}, {"url": "https://ftp.postgresql.org/pub/source/v18.6/postgresql-18.6.tar.bz2", "label": "Matching PostgreSQL source archive", "sha256": "555610c24d53e4316da5b7d3fc25c279d96856d5e0e23ee308c328c5fa881d9f"}], "coverage": "source inventory; exact declared input types for operator classes", "sections": [], "operators": [], "signature": "fdw_handler", "description": ["A foreign-data wrapper handler is declared to return fdw_handler ."], "manual_html": "
\n
\n
\n
\n

8.21. Pseudo-Types

\n
\n
\n
\n

The PostgreSQL type system contains a number of special-purpose entries that are collectively called pseudo-types. A pseudo-type cannot be used as a column data type, but it can be used to declare a function's argument or result type. Each of the available pseudo-types is useful in situations where a function's behavior does not correspond to simply taking or returning a value of a specific SQL data type. Table 8.27 lists the existing pseudo-types.

\n
\n

Table 8.27. Pseudo-Types

\n
\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
NameDescription
anyIndicates that a function accepts any input data type.
anyelementIndicates that a function accepts any data type (see Section 36.2.5).
anyarrayIndicates that a function accepts any array data type (see Section 36.2.5).
anynonarrayIndicates that a function accepts any non-array data type (see Section 36.2.5).
anyenumIndicates that a function accepts any enum data type (see Section 36.2.5 and Section 8.7).
anyrangeIndicates that a function accepts any range data type (see Section 36.2.5 and Section 8.17).
anymultirangeIndicates that a function accepts any multirange data type (see Section 36.2.5 and Section 8.17).
anycompatibleIndicates that a function accepts any data type, with automatic promotion of multiple arguments to a common data type (see Section 36.2.5).
anycompatiblearrayIndicates that a function accepts any array data type, with automatic promotion of multiple arguments to a common data type (see Section 36.2.5).
anycompatiblenonarrayIndicates that a function accepts any non-array data type, with automatic promotion of multiple arguments to a common data type (see Section 36.2.5).
anycompatiblerangeIndicates that a function accepts any range data type, with automatic promotion of multiple arguments to a common data type (see Section 36.2.5 and Section 8.17).
anycompatiblemultirangeIndicates that a function accepts any multirange data type, with automatic promotion of multiple arguments to a common data type (see Section 36.2.5 and Section 8.17).
cstringIndicates that a function accepts or returns a null-terminated C string.
internalIndicates that a function accepts or returns a server-internal data type.
language_handlerA procedural language call handler is declared to return language_handler.
fdw_handlerA foreign-data wrapper handler is declared to return fdw_handler.
table_am_handlerA table access method handler is declared to return table_am_handler.
index_am_handlerAn index access method handler is declared to return index_am_handler.
tsm_handlerA tablesample method handler is declared to return tsm_handler.
recordIdentifies a function taking or returning an unspecified row type.
triggerA trigger function is declared to return trigger.
event_triggerAn event trigger function is declared to return event_trigger.
pg_ddl_commandIdentifies a representation of DDL commands that is available to event triggers.
voidIndicates that a function returns no value.
unknownIdentifies a not-yet-resolved type, e.g., of an undecorated string literal.
\n
\n

\n

Functions coded in C (whether built-in or dynamically loaded) can be declared to accept or return any of these pseudo-types. It is up to the function author to ensure that the function will behave safely when a pseudo-type is used as an argument type.

\n

Functions coded in procedural languages can use pseudo-types only as allowed by their implementation languages. At present most procedural languages forbid use of a pseudo-type as an argument type, and allow only void and record as a result type (plus trigger or event_trigger when the function is used as a trigger or event trigger). Some also support polymorphic functions using the polymorphic pseudo-types, which are shown above and discussed in detail in Section 36.2.5.

\n

The internal pseudo-type is used to declare functions that are meant only to be called internally by the database system, and not by direct invocation in an SQL query. If a function has at least one internal-type argument then it cannot be called from SQL. To preserve the type safety of this restriction it is important to follow this coding rule: do not create any function that is declared to return internal unless it has at least one internal argument.

\n
", "manual_path": "datatype-pseudo.html", "comparison_data": {"casts": [], "facts": [{"label": "Catalog name", "value": "pg_catalog.fdw_handler"}, {"label": "Declared length", "value": "4 bytes"}, {"label": "Documented declaration", "value": "fdw_handler"}, {"label": "Input function", "value": "fdw_handler_in"}, {"label": "Output function", "value": "fdw_handler_out"}, {"label": "Storage strategy", "value": "plain"}, {"label": "Type OID", "value": "3115"}, {"label": "Type kind", "value": "Pseudo-type"}], "ranges": [], "aliases": [], "catalog": {"typacl": "_null_", "typlen": "4", "typelem": "0", "typname": "fdw_handler", "typsend": "-", "typtype": "p", "typalign": "i", "typarray": "", "typbyval": "t", "typdelim": ",", "typinput": "fdw_handler_in", "typmodin": "-", "typndims": "0", "typrelid": "0", "typmodout": "-", "typoutput": "fdw_handler_out", "typtypmod": "-1", "typanalyze": "-", "typdefault": "_null_", "typnotnull": "f", "typreceive": "-", "typstorage": "p", "typbasetype": "0", "typcategory": "P", "typcollation": "0", "typisdefined": "t", "typsubscript": "-", "typdefaultbin": "_null_", "typispreferred": "f", "array_type_name": ""}, "operators": [], "operator_classes": []}, "comparison_hash": "d8ee82eabbdfea4b78e996b059ebdd0dd23d558456825846d16287f6f5149c7c", "operator_classes": [], "manual_documentation": "dedicated family chapter"}, "from": "17", "comparison": {"available": true, "changes": [], "prose_changed": true}}