pg_language registers call interfaces or languages in which you can write functions or stored procedures. See under CREATE LANGUAGE and in the Programmer's Guide for more information about language handlers.
Table 3-18. pg_language Columns
|lanname||name||Name of the language (to be specified when creating a function)|
|lanispl||bool||This is false for internal languages (such as SQL) and true for user-defined languages. Currently, pg_dump still uses this to determine which languages need to be dumped, but this may be replaced by a different mechanism sometime.|
|lanpltrusted||bool||This is a trusted language. See under CREATE LANGUAGE what this means. If this is an internal language (lanispl is false) then this field is meaningless.|
|lanplcallfoid||oid||pg_proc.oid||For non-internal languages this references the language handler, which is a special function that is responsible for executing all functions that are written in the particular language.|
|lanvalidator||oid||pg_proc.oid||This references a language validator function that is responsible for checking the syntax and validity of new functions when they are created. See under CREATE LANGUAGE for further information about validators.|
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