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, 107 insertions, 9 deletions

diff --git a/src/backend/executor/spi.c b/src/backend/executor/spi.c
index eeaa4805e4d..54c022d0132 100644
--- a/src/backend/executor/spi.c
+++ b/src/backend/executor/spi.c
@@ -122,6 +122,7 @@ SPI_connect(void)
 	_SPI_current->procCxt = NULL;		/* in case we fail to create 'em */
 	_SPI_current->execCxt = NULL;
 	_SPI_current->connectSubid = GetCurrentSubTransactionId();
+	_SPI_current->queryEnv = NULL;
 
 	/*
 	 * Create memory contexts for this procedure
@@ -1193,7 +1194,7 @@ SPI_cursor_open_internal(const char *name, SPIPlanPtr plan,
 	 */
 
 	/* Replan if needed, and increment plan refcount for portal */
-	cplan = GetCachedPlan(plansource, paramLI, false);
+	cplan = GetCachedPlan(plansource, paramLI, false, _SPI_current->queryEnv);
 	stmt_list = cplan->stmt_list;
 
 	/* Pop the error context stack */
@@ -1532,6 +1533,10 @@ SPI_result_code_string(int code)
 			return "SPI_ERROR_NOOUTFUNC";
 		case SPI_ERROR_TYPUNKNOWN:
 			return "SPI_ERROR_TYPUNKNOWN";
+		case SPI_ERROR_REL_DUPLICATE:
+			return "SPI_ERROR_REL_DUPLICATE";
+		case SPI_ERROR_REL_NOT_FOUND:
+			return "SPI_ERROR_REL_NOT_FOUND";
 		case SPI_OK_CONNECT:
 			return "SPI_OK_CONNECT";
 		case SPI_OK_FINISH:
@@ -1560,6 +1565,10 @@ SPI_result_code_string(int code)
 			return "SPI_OK_UPDATE_RETURNING";
 		case SPI_OK_REWRITTEN:
 			return "SPI_OK_REWRITTEN";
+		case SPI_OK_REL_REGISTER:
+			return "SPI_OK_REL_REGISTER";
+		case SPI_OK_REL_UNREGISTER:
+			return "SPI_OK_REL_UNREGISTER";
 	}
 	/* Unrecognized code ... return something useful ... */
 	sprintf(buf, "Unrecognized SPI code %d", code);
@@ -1615,7 +1624,8 @@ SPI_plan_get_cached_plan(SPIPlanPtr plan)
 	error_context_stack = &spierrcontext;
 
 	/* Get the generic plan for the query */
-	cplan = GetCachedPlan(plansource, NULL, plan->saved);
+	cplan = GetCachedPlan(plansource, NULL, plan->saved,
+						  _SPI_current->queryEnv);
 	Assert(cplan == plansource->gplan);
 
 	/* Pop the error context stack */
@@ -1767,7 +1777,8 @@ _SPI_prepare_plan(const char *src, SPIPlanPtr plan)
 		 */
 		plansource = CreateCachedPlan(parsetree,
 									  src,
-									  CreateCommandTag(parsetree->stmt));
+									  CreateCommandTag(parsetree->stmt),
+									  _SPI_current->queryEnv);
 
 		/*
 		 * Parameter datatypes are driven by parserSetup hook if provided,
@@ -1779,14 +1790,16 @@ _SPI_prepare_plan(const char *src, SPIPlanPtr plan)
 			stmt_list = pg_analyze_and_rewrite_params(parsetree,
 													  src,
 													  plan->parserSetup,
-													  plan->parserSetupArg);
+													  plan->parserSetupArg,
+													  _SPI_current->queryEnv);
 		}
 		else
 		{
 			stmt_list = pg_analyze_and_rewrite(parsetree,
 											   src,
 											   plan->argtypes,
-											   plan->nargs);
+											   plan->nargs,
+											   _SPI_current->queryEnv);
 		}
 
 		/* Finish filling in the CachedPlanSource */
@@ -1975,14 +1988,16 @@ _SPI_execute_plan(SPIPlanPtr plan, ParamListInfo paramLI,
 				stmt_list = pg_analyze_and_rewrite_params(parsetree,
 														  src,
 														  plan->parserSetup,
-													   plan->parserSetupArg);
+													   plan->parserSetupArg,
+													  _SPI_current->queryEnv);
 			}
 			else
 			{
 				stmt_list = pg_analyze_and_rewrite(parsetree,
 												   src,
 												   plan->argtypes,
-												   plan->nargs);
+												   plan->nargs,
+												   _SPI_current->queryEnv);
 			}
 
 			/* Finish filling in the CachedPlanSource */
@@ -2001,7 +2016,7 @@ _SPI_execute_plan(SPIPlanPtr plan, ParamListInfo paramLI,
 		 * Replan if needed, and increment plan refcount.  If it's a saved
 		 * plan, the refcount must be backed by the CurrentResourceOwner.
 		 */
-		cplan = GetCachedPlan(plansource, paramLI, plan->saved);
+		cplan = GetCachedPlan(plansource, paramLI, plan->saved, _SPI_current->queryEnv);
 		stmt_list = cplan->stmt_list;
 
 		/*
@@ -2081,7 +2096,8 @@ _SPI_execute_plan(SPIPlanPtr plan, ParamListInfo paramLI,
 										plansource->query_string,
 										snap, crosscheck_snapshot,
 										dest,
-										paramLI, 0);
+										paramLI, _SPI_current->queryEnv,
+										0);
 				res = _SPI_pquery(qdesc, fire_triggers,
 								  canSetTag ? tcount : 0);
 				FreeQueryDesc(qdesc);
@@ -2094,6 +2110,7 @@ _SPI_execute_plan(SPIPlanPtr plan, ParamListInfo paramLI,
 							   plansource->query_string,
 							   PROCESS_UTILITY_QUERY,
 							   paramLI,
+							   _SPI_current->queryEnv,
 							   dest,
 							   completionTag);
 
@@ -2619,3 +2636,84 @@ _SPI_save_plan(SPIPlanPtr plan)
 
 	return newplan;
 }
+
+/*
+ * Internal lookup of ephemeral named relation by name.
+ */
+static EphemeralNamedRelation
+_SPI_find_ENR_by_name(const char *name)
+{
+	/* internal static function; any error is bug in SPI itself */
+	Assert(name != NULL);
+
+	/* fast exit if no tuplestores have been added */
+	if (_SPI_current->queryEnv == NULL)
+		return NULL;
+
+	return get_ENR(_SPI_current->queryEnv, name);
+}
+
+/*
+ * Register an ephemeral named relation for use by the planner and executor on
+ * subsequent calls using this SPI connection.
+ */
+int
+SPI_register_relation(EphemeralNamedRelation enr)
+{
+	EphemeralNamedRelation match;
+	int			res;
+
+	if (enr == NULL || enr->md.name == NULL)
+		return SPI_ERROR_ARGUMENT;
+
+	res = _SPI_begin_call(false);	/* keep current memory context */
+	if (res < 0)
+		return res;
+
+	match = _SPI_find_ENR_by_name(enr->md.name);
+	if (match)
+		res = SPI_ERROR_REL_DUPLICATE;
+	else
+	{
+		if (_SPI_current->queryEnv == NULL)
+			_SPI_current->queryEnv = create_queryEnv();
+
+		register_ENR(_SPI_current->queryEnv, enr);
+		res = SPI_OK_REL_REGISTER;
+	}
+
+	_SPI_end_call(false);
+
+	return res;
+}
+
+/*
+ * Unregister an ephemeral named relation by name.  This will probably be a
+ * rarely used function, since SPI_finish will clear it automatically.
+ */
+int
+SPI_unregister_relation(const char *name)
+{
+	EphemeralNamedRelation match;
+	int			res;
+
+	if (name == NULL)
+		return SPI_ERROR_ARGUMENT;
+
+	res = _SPI_begin_call(false);	/* keep current memory context */
+	if (res < 0)
+		return res;
+
+	match = _SPI_find_ENR_by_name(name);
+	if (match)
+	{
+		unregister_ENR(_SPI_current->queryEnv, match->md.name);
+		res = SPI_OK_REL_UNREGISTER;
+	}
+	else
+		res = SPI_ERROR_REL_NOT_FOUND;
+
+	_SPI_end_call(false);
+
+	return res;
+}