A custom scan provider will typically add paths for a base relation by

setting the following hook, which is called after the core code has

generated all the access paths it can for the relation (except for

Gather paths, which are made after this call so that they can use

partial paths added by the hook):

Gatherand Gather Mergepaths, which are made after this call so that

they can usepartial paths added by the hook):

<programlisting>

typedef void (*set_rel_pathlist_hook_type) (PlannerInfo *root,

RelOptInfo *rel,

Although this hook function can be used to examine, modify, or remove

paths generated by the core system, a custom scan provider will typically

confine itself to generating <structname>CustomPath</structname> objects and adding

them to <literal>rel</literal> using <function>add_path</function>. The custom scan

provider is responsible for initializing the <structname>CustomPath</structname>

object, which is declared like this:

them to <literal>rel</literal> using <function>add_path</function>, or

<function>add_partial_path</function> if they are partial paths. The

custom scan provider is responsible for initializing the

<structname>CustomPath</structname> object, which is declared like this:

<programlisting>

typedef struct CustomPath

{