| title | summary | toc |
|---|---|---|
Name Resolution |
Table and function names can exist in multiple places. Resolution decides which one to use. |
false |
A SQL client can have access to multiple databases side-by-side. The
same table name, e.g. orders, can exist in multiple
databases. When a query specifies a table name without a database
name, for example, select * from orders, how does CockroachDB know
which orders table is being considered?
This page details how CockroachDB performs name resolution to answer this question.
The following name resolution algorithm is used both to determine table names in table expressions and function names in value expressions:
- If the given name already tells where to look explicitly, i.e. it is qualified, then just use this information.
- Otherwise, i.e. the name is unqualified:
- Try to find the name in the "default database" as set by
SET DATABASE. - Try to find the name using the search path.
- If the name was not found so far, produce an error.
- Try to find the name in the "default database" as set by
In addition to the default database configurable via SET DATABASE,
unqualified names are also looked up in the current session's search path.
The search path is a session variable containing a list of databases, or name spaces, where names are looked up.
The current search path can be inspected using the statement SHOW SEARCH_PATH, or SHOW ALL.
Every new session has a search path initialized to a single item:
pg_catalog, so that queries can use PostgreSQL compatibility
functions and virtual tables in that namespace without the need to
prefix them with "pg_catalog." every time.