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pg_include/executor/spi_priv.h

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+/*-------------------------------------------------------------------------
+ *
+ * spi_priv.h
+ *				Server Programming Interface private declarations
+ *
+ * Portions Copyright (c) 1996-2012, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/executor/spi_priv.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef SPI_PRIV_H
+#define SPI_PRIV_H
+
+#include "executor/spi.h"
+
+
+#define _SPI_PLAN_MAGIC		569278163
+
+typedef struct
+{
+	/* current results */
+	uint32		processed;		/* by Executor */
+	Oid			lastoid;
+	SPITupleTable *tuptable;
+
+	MemoryContext procCxt;		/* procedure context */
+	MemoryContext execCxt;		/* executor context */
+	MemoryContext savedcxt;		/* context of SPI_connect's caller */
+	SubTransactionId connectSubid;		/* ID of connecting subtransaction */
+} _SPI_connection;
+
+/*
+ * SPI plans have three states: saved, unsaved, or temporary.
+ *
+ * Ordinarily, the _SPI_plan struct itself as well as the argtypes array
+ * are in a dedicated memory context identified by plancxt (which can be
+ * really small).  All the other subsidiary state is in plancache entries
+ * identified by plancache_list (note: the list cells themselves are in
+ * plancxt).
+ *
+ * In an unsaved plan, the plancxt as well as the plancache entries' contexts
+ * are children of the SPI procedure context, so they'll all disappear at
+ * function exit.  plancache.c also knows that the plancache entries are
+ * "unsaved", so it doesn't link them into its global list; hence they do
+ * not respond to inval events.  This is OK since we are presumably holding
+ * adequate locks to prevent other backends from messing with the tables.
+ *
+ * For a saved plan, the plancxt is made a child of CacheMemoryContext
+ * since it should persist until explicitly destroyed.	Likewise, the
+ * plancache entries will be under CacheMemoryContext since we tell
+ * plancache.c to save them.  We rely on plancache.c to keep the cache
+ * entries up-to-date as needed in the face of invalidation events.
+ *
+ * There are also "temporary" SPI plans, in which the _SPI_plan struct is
+ * not even palloc'd but just exists in some function's local variable.
+ * The plancache entries are unsaved and exist under the SPI executor context,
+ * while additional data such as argtypes and list cells is loose in the SPI
+ * executor context.  Such plans can be identified by having plancxt == NULL.
+ *
+ * We can also have "one-shot" SPI plans (which are typically temporary,
+ * as described above).  These are meant to be executed once and discarded,
+ * and various optimizations are made on the assumption of single use.
+ * Note in particular that the CachedPlanSources within such an SPI plan
+ * are not "complete" until execution.
+ *
+ * Note: if the original query string contained only whitespace and comments,
+ * the plancache_list will be NIL and so there is no place to store the
+ * query string.  We don't care about that, but we do care about the
+ * argument type array, which is why it's seemingly-redundantly stored.
+ */
+typedef struct _SPI_plan
+{
+	int			magic;			/* should equal _SPI_PLAN_MAGIC */
+	bool		saved;			/* saved or unsaved plan? */
+	bool		oneshot;		/* one-shot plan? */
+	List	   *plancache_list; /* one CachedPlanSource per parsetree */
+	MemoryContext plancxt;		/* Context containing _SPI_plan and data */
+	int			cursor_options; /* Cursor options used for planning */
+	int			nargs;			/* number of plan arguments */
+	Oid		   *argtypes;		/* Argument types (NULL if nargs is 0) */
+	ParserSetupHook parserSetup;	/* alternative parameter spec method */
+	void	   *parserSetupArg;
+} _SPI_plan;
+
+#endif   /* SPI_PRIV_H */