Question 161765 in PostgreSQL Question posted in
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What is SET search_path’s purpose in PostgreSQL?

I was working with Apache AGE and I came across a code:

SET search_path = ag_catalog, "$user", public;

Could someone explain what is the meaning of all three parts of the code? Also what other values can these take?

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  1. 0

    This is basically used to set the search PATH in Apache Age.
    The ‘search_path’ is a variable that determines the order in which database schemas are searched for objects.

    'ag_catalog' : Here Apache age store its systems catalogs and metadata.

    "$user" : This refer to schema that has name as current user.

     'public':

    and this refer default schema in Apache age that accessible to all users.

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  2. 0

    The use of SET search_path here is to set the ‘ag_catalog’ schema to create objects into the schema by default. The three variables that are assigned are all schemas that are ordered based on the precedence determined by the user.

    ag_catalog is a schema with AGE system catalogs, "$user" is the schema of the same name as the current user, and public is the default public schema.

    Also whenever objects are referenced, the search path is traversed until the matching object is found.

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  3. 0

    The SET search_path command is used to set the default schema search path for a session. It allows you to specify the order of schemas to search for unqualified object names, such as tables and views. This is useful when you have multiple schemas in your database and want to avoid having to fully qualify object names in your queries.

    So in Apache Age you have to use the command;

    SET search_path = ag_catalog, "$user", public;
    So you can specify the schema to search for, in this case (ag_catalog), with $user being the current user, and public representing the default schema in PostgreSQL.

    If not, in order to perform simple queries such creating a graph;

    SELECT * FROM create_graph('sales');

    You would have to write longer queries;

    SELECT * FROM ag_catalog.create_graph('sales');

    In other words, adding ag_catalog to your search_path will help simplify your queries.

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  4. 0

    The SET search_path command is used to set the default schema search path for a session in PostgreSQL. In Apache Age, this command is also used to specify the order of schemas to search for unqualified object names, such as tables and views.

    When you have multiple schemas in your database, specifying a search path can save you from having to fully qualify object names in your queries. This makes queries more efficient and easier to write.

    To specify the schema to search for in Apache Age, you can use the following command:

    SET search_path = ag_catalog, "$user", public;

    This command sets the search path to look for objects in the ag_catalog schema first, followed by the current user’s schema (represented by $user), and then the public schema. The public schema is the default schema in PostgreSQL.

    By adding ag_catalog to your search path, you can simplify queries. For example, instead of writing:

    SELECT * FROM ag_catalog.create_graph('Graph_Name');

    You can simply write:

    SELECT * FROM create_graph('Graph_Name');

    This is because the search path includes ag_catalog as the first schema to search for unqualified object names.

    Overall, using SET search_path in Apache Age can help you write more efficient and concise queries by specifying the order of schemas to search for unqualified object names.

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  5. 0

    This command is used to set the order in which the database looks for tables and other objects when they are referenced in a query.

    ag_catalog is specific to Apache AGE and contains catalog tables for the graph database;

    "$user", is a placeholder for the current user’s own schema; and

    public, is the default schema accessible to all users.

    You can change the search path to include different schemas or modify the order of schema resolution based on what you need.

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