This is needed to avoid syntactic ambiguity. If you need to write a qualified operator name in an expression, there is a special provision: you must write OPERATOR( schema.
Data type and function names can be qualified in exactly the same way as table names. The search path works in the same way for data type names, function names, and operator names as it does for table names. See also Section 9.26 for other ways to manipulate the schema search path. There is nothing special about the public schema except that it exists by default.
Then we no longer have access to the public schema without explicit qualification. (We omit the $user here because we have no immediate need for it.) And then we can access the table without schema qualification:Īlso, since myschema is the first element in the path, new objects would by default be created in it. To put our new schema in the path, we use: Therefore, in the default configuration, any unqualified access again can only refer to the public schema. When objects are referenced in any other context without schema qualification (table modification, data modification, or query commands) the search path is traversed until a matching object is found. That is the reason that by default objects are created in the public schema. The first schema in the search path that exists is the default location for creating new objects. The second element refers to the public schema that we have seen already. If no such schema exists, the entry is ignored. The first element specifies that a schema with the same name as the current user is to be searched. To show the current search path, use the following command: Aside from being the first schema searched, it is also the schema in which new tables will be created if the CREATE TABLE command does not specify a schema name. The first schema named in the search path is called the current schema. When you run an ordinary query, a malicious user able to create objects in a schema of your search path can take control and execute arbitrary SQL functions as though you executed them. Due to the prevalence of unqualified names in queries and their use in PostgreSQL internals, adding a schema to search_path effectively trusts all users having CREATE privilege on that schema. It also opens up the potential for users to change the behavior of other users' queries, maliciously or accidentally. The ability to create like-named objects in different schemas complicates writing a query that references precisely the same objects every time. If there is no match in the search path, an error is reported, even if matching table names exist in other schemas in the database. The first matching table in the search path is taken to be the one wanted. The system determines which table is meant by following a search path, which is a list of schemas to look in. Therefore tables are often referred to by unqualified names, which consist of just the table name. Qualified names are tedious to write, and it's often best not to wire a particular schema name into applications anyway. Schema names beginning with pg_ are reserved for system purposes and cannot be created by users. See Section 5.9.6 for how this can be useful.
You can even omit the schema name, in which case the schema name will be the same as the user name. The syntax for that is:ĬREATE SCHEMA schema_name AUTHORIZATION user_name Often you will want to create a schema owned by someone else (since this is one of the ways to restrict the activities of your users to well-defined namespaces). See Section 5.14 for a description of the general mechanism behind this. To drop a schema including all contained objects, use: To drop a schema if it's empty (all objects in it have been dropped), use: So to create a table in the new schema, use: If you write a database name, it must be the same as the database you are connected to.
#Xsection 9.5 pro
tableĬan be used too, but at present this is just for pro forma compliance with the SQL standard. (For brevity we will speak of tables only, but the same ideas apply to other kinds of named objects, such as types and functions.)Īctually, the even more general syntax database. This works anywhere a table name is expected, including the table modification commands and the data access commands discussed in the following chapters. To create or access objects in a schema, write a qualified name consisting of the schema name and table name separated by a dot: schema. To create a schema, use the CREATE SCHEMA command.
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