database.mod/postgresql.mod/include/utils/queryenvironment.h

/*-------------------------------------------------------------------------
 *
 * queryenvironment.h
 *	  Access to functions to mutate the query environment and retrieve the
 *	  actual data related to entries (if any).
 *
 * Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/utils/queryenvironment.h
 *
 *-------------------------------------------------------------------------
 */
#ifndef QUERYENVIRONMENT_H
#define QUERYENVIRONMENT_H

#include "access/tupdesc.h"


typedef enum EphemeralNameRelationType
{
	ENR_NAMED_TUPLESTORE		/* named tuplestore relation; e.g., deltas */
} EphemeralNameRelationType;

/*
 * Some ephemeral named relations must match some relation (e.g., trigger
 * transition tables), so to properly handle cached plans and DDL, we should
 * carry the OID of that relation.  In other cases an ENR might be independent
 * of any relation which is stored in the system catalogs, so we need to be
 * able to directly store the TupleDesc.  We never need both.
 */
typedef struct EphemeralNamedRelationMetadataData
{
	char	   *name;			/* name used to identify the relation */

	/* only one of the next two fields should be used */
	Oid			reliddesc;		/* oid of relation to get tupdesc */
	TupleDesc	tupdesc;		/* description of result rows */

	EphemeralNameRelationType enrtype;	/* to identify type of relation */
	double		enrtuples;		/* estimated number of tuples */
} EphemeralNamedRelationMetadataData;

typedef EphemeralNamedRelationMetadataData *EphemeralNamedRelationMetadata;

/*
 * Ephemeral Named Relation data; used for parsing named relations not in the
 * catalog, like transition tables in AFTER triggers.
 */
typedef struct EphemeralNamedRelationData
{
	EphemeralNamedRelationMetadataData md;
	void	   *reldata;		/* structure for execution-time access to data */
} EphemeralNamedRelationData;

typedef EphemeralNamedRelationData *EphemeralNamedRelation;

/*
 * This is an opaque structure outside of queryenvironment.c itself.  The
 * intention is to be able to change the implementation or add new context
 * features without needing to change existing code for use of existing
 * features.
 */
typedef struct QueryEnvironment QueryEnvironment;


extern QueryEnvironment *create_queryEnv(void);
extern EphemeralNamedRelationMetadata get_visible_ENR_metadata(QueryEnvironment *queryEnv, const char *refname);
extern void register_ENR(QueryEnvironment *queryEnv, EphemeralNamedRelation enr);
extern void unregister_ENR(QueryEnvironment *queryEnv, const char *name);
extern EphemeralNamedRelation get_ENR(QueryEnvironment *queryEnv, const char *name);
extern TupleDesc ENRMetadataGetTupDesc(EphemeralNamedRelationMetadata enrmd);

#endif							/* QUERYENVIRONMENT_H */