Add infrastructure to support EphemeralNamedRelation references.

A QueryEnvironment concept is added, which allows new types of
objects to be passed into queries from parsing on through
execution.  At this point, the only thing implemented is a
collection of EphemeralNamedRelation objects -- relations which
can be referenced by name in queries, but do not exist in the
catalogs.  The only type of ENR implemented is NamedTuplestore, but
provision is made to add more types fairly easily.

An ENR can carry its own TupleDesc or reference a relation in the
catalogs by relid.

Although these features can be used without SPI, convenience
functions are added to SPI so that ENRs can easily be used by code
run through SPI.

The initial use of all this is going to be transition tables in
AFTER triggers, but that will be added to each PL as a separate
commit.

An incidental effect of this patch is to produce a more informative
error message if an attempt is made to modify the contents of a CTE
from a referencing DML statement.  No tests previously covered that
possibility, so one is added.

Kevin Grittner and Thomas Munro
Reviewed by Heikki Linnakangas, David Fetter, and Thomas Munro
with valuable comments and suggestions from many others

4 files changed, 84 insertions, 3 deletions

diff --git a/src/include/utils/plancache.h b/src/include/utils/plancache.h
index 84952d56e70..48d4ac94b2a 100644
--- a/src/include/utils/plancache.h
+++ b/src/include/utils/plancache.h
@@ -17,6 +17,7 @@
 
 #include "access/tupdesc.h"
 #include "nodes/params.h"
+#include "utils/queryenvironment.h"
 
 /* Forward declaration, to avoid including parsenodes.h here */
 struct RawStmt;
@@ -148,7 +149,8 @@ extern void ResetPlanCache(void);
 
 extern CachedPlanSource *CreateCachedPlan(struct RawStmt *raw_parse_tree,
 				 const char *query_string,
-				 const char *commandTag);
+				 const char *commandTag,
+				 QueryEnvironment *queryEnv);
 extern CachedPlanSource *CreateOneShotCachedPlan(struct RawStmt *raw_parse_tree,
 						const char *query_string,
 						const char *commandTag);
@@ -172,11 +174,13 @@ extern CachedPlanSource *CopyCachedPlan(CachedPlanSource *plansource);
 
 extern bool CachedPlanIsValid(CachedPlanSource *plansource);
 
-extern List *CachedPlanGetTargetList(CachedPlanSource *plansource);
+extern List *CachedPlanGetTargetList(CachedPlanSource *plansource,
+							QueryEnvironment *queryEnv);
 
 extern CachedPlan *GetCachedPlan(CachedPlanSource *plansource,
 			  ParamListInfo boundParams,
-			  bool useResOwner);
+			  bool useResOwner,
+			  QueryEnvironment *queryEnv);
 extern void ReleaseCachedPlan(CachedPlan *plan, bool useResOwner);
 
 #endif   /* PLANCACHE_H */
diff --git a/src/include/utils/portal.h b/src/include/utils/portal.h
index e7c5a8bd091..ef3898c98cb 100644
--- a/src/include/utils/portal.h
+++ b/src/include/utils/portal.h
@@ -137,6 +137,7 @@ typedef struct PortalData
 	CachedPlan *cplan;			/* CachedPlan, if stmts are from one */
 
 	ParamListInfo portalParams; /* params to pass to query */
+	QueryEnvironment *queryEnv; /* environment for query */
 
 	/* Features/options */
 	PortalStrategy strategy;	/* see above */
diff --git a/src/include/utils/queryenvironment.h b/src/include/utils/queryenvironment.h
new file mode 100644
index 00000000000..b4f65a19768
--- /dev/null
+++ b/src/include/utils/queryenvironment.h
@@ -0,0 +1,74 @@
+/*-------------------------------------------------------------------------
+ *
+ * queryenvironment.h
+ *	  Access to functions to mutate the query environment and retrieve the
+ *	  actual data related to entries (if any).
+ *
+ * Portions Copyright (c) 1996-2017, 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 */
diff --git a/src/include/utils/tuplestore.h b/src/include/utils/tuplestore.h
index a52a5470372..b31ede882b9 100644
--- a/src/include/utils/tuplestore.h
+++ b/src/include/utils/tuplestore.h
@@ -78,6 +78,8 @@ extern bool tuplestore_advance(Tuplestorestate *state, bool forward);
 extern bool tuplestore_skiptuples(Tuplestorestate *state,
 					  int64 ntuples, bool forward);
 
+extern int64 tuplestore_tuple_count(Tuplestorestate *state);
+
 extern bool tuplestore_ateof(Tuplestorestate *state);
 
 extern void tuplestore_rescan(Tuplestorestate *state);