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db_include/utils/queryenvironment.h

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+/*-------------------------------------------------------------------------
+ *
+ * queryenvironment.h
+ *	  Access to functions to mutate the query environment and retrieve the
+ *	  actual data related to entries (if any).
+ *
+ * Portions Copyright (c) 1996-2021, 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 */