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

1 files changed, 21 insertions, 0 deletions

diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index 11a68500eea..fa992449f47 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -22,6 +22,7 @@
 #include "nodes/params.h"
 #include "nodes/plannodes.h"
 #include "utils/hsearch.h"
+#include "utils/queryenvironment.h"
 #include "utils/reltrigger.h"
 #include "utils/sortsupport.h"
 #include "utils/tuplestore.h"
@@ -431,6 +432,8 @@ typedef struct EState
 	ParamListInfo es_param_list_info;	/* values of external params */
 	ParamExecData *es_param_exec_vals;	/* values of internal params */
 
+	QueryEnvironment *es_queryEnv;	/* query environment */
+
 	/* Other working state: */
 	MemoryContext es_query_cxt; /* per-query context in which EState lives */
 
@@ -1446,6 +1449,24 @@ typedef struct CteScanState
 } CteScanState;
 
 /* ----------------
+ *	 NamedTuplestoreScanState information
+ *
+ *		NamedTuplestoreScan nodes are used to scan a Tuplestore created and
+ *		named prior to execution of the query.  An example is a transition
+ *		table for an AFTER trigger.
+ *
+ * Multiple NamedTuplestoreScan nodes can read out from the same Tuplestore.
+ * ----------------
+ */
+typedef struct NamedTuplestoreScanState
+{
+	ScanState	ss;				/* its first field is NodeTag */
+	int			readptr;		/* index of my tuplestore read pointer */
+	TupleDesc	tupdesc;		/* format of the tuples in the tuplestore */
+	Tuplestorestate *relation;	/* the rows */
+} NamedTuplestoreScanState;
+
+/* ----------------
  *	 WorkTableScanState information
  *
  *		WorkTableScan nodes are used to scan the work table created by