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 (e.g., 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.

Overview

The following name resolution algorithm is used both to determine table names in table expressions and function names in value expressions:

  • If the name is qualified (i.e., the name already tells where to look), use this information. For example, SELECT * FROM db1.orders will look up "orders" only in db1.
  • If 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 is not found, produce an error.

Search Path

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 namespaces, where names are looked up.

The current search path can set using SET SEARCH_PATH and can be inspected using SHOW SEARCH_PATH or SHOW ALL.

By default, the search path for new columns includes just 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.

See Also



Yes No