pg_cast.h

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/*-------------------------------------------------------------------------
 *
 * pg_cast.h
 *    definition of the "type casts" system catalog (pg_cast)
 *
 * As of Postgres 8.0, pg_cast describes not only type coercion functions
 * but also length coercion functions.
 *
 * Portions Copyright (c) 1996-2020, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/catalog/pg_cast.h
 *
 * NOTES
 *    The Catalog.pm module reads this file and derives schema
 *    information.
 *
 *-------------------------------------------------------------------------
 */
#ifndef PG_CAST_H
#define PG_CAST_H

#include "catalog/dependency.h"
#include "catalog/genbki.h"
#include "catalog/pg_cast_d.h"

/* ----------------
 *      pg_cast definition.  cpp turns this into
 *      typedef struct FormData_pg_cast
 * ----------------
 */
CATALOG(pg_cast,2605,CastRelationId)
{
    Oid         oid;            /* oid */

    /* source datatype for cast */
    Oid         castsource BKI_LOOKUP(pg_type);

    /* destination datatype for cast */
    Oid         casttarget BKI_LOOKUP(pg_type);

    /* cast function; 0 = binary coercible */
    Oid         castfunc BKI_LOOKUP(pg_proc);

    /* contexts in which cast can be used */
    char        castcontext;

    /* cast method */
    char        castmethod;
} FormData_pg_cast;

/* ----------------
 *      Form_pg_cast corresponds to a pointer to a tuple with
 *      the format of pg_cast relation.
 * ----------------
 */
typedef FormData_pg_cast *Form_pg_cast;

#ifdef EXPOSE_TO_CLIENT_CODE

/*
 * The allowable values for pg_cast.castcontext are specified by this enum.
 * Since castcontext is stored as a "char", we use ASCII codes for human
 * convenience in reading the table.  Note that internally to the backend,
 * these values are converted to the CoercionContext enum (see primnodes.h),
 * which is defined to sort in a convenient order; the ASCII codes don't
 * have to sort in any special order.
 */

typedef enum CoercionCodes
{
    COERCION_CODE_IMPLICIT = 'i',   /* coercion in context of expression */
    COERCION_CODE_ASSIGNMENT = 'a', /* coercion in context of assignment */
    COERCION_CODE_EXPLICIT = 'e'    /* explicit cast operation */
} CoercionCodes;

/*
 * The allowable values for pg_cast.castmethod are specified by this enum.
 * Since castmethod is stored as a "char", we use ASCII codes for human
 * convenience in reading the table.
 */
typedef enum CoercionMethod
{
    COERCION_METHOD_FUNCTION = 'f', /* use a function */
    COERCION_METHOD_BINARY = 'b',   /* types are binary-compatible */
    COERCION_METHOD_INOUT = 'i' /* use input/output functions */
} CoercionMethod;

#endif                          /* EXPOSE_TO_CLIENT_CODE */


extern ObjectAddress CastCreate(Oid sourcetypeid,
                                Oid targettypeid,
                                Oid funcid,
                                char castcontext,
                                char castmethod,
                                DependencyType behavior);

#endif                          /* PG_CAST_H */