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e6faf910d7
Rewrite plancache.c so that a "cached plan" (which is rather a misnomer at this point) can support generation of custom, parameter-value-dependent plans, and can make an intelligent choice between using custom plans and the traditional generic-plan approach. The specific choice algorithm implemented here can probably be improved in future, but this commit is all about getting the mechanism in place, not the policy. In addition, restructure the API to greatly reduce the amount of extraneous data copying needed. The main compromise needed to make that possible was to split the initial creation of a CachedPlanSource into two steps. It's worth noting in particular that SPI_saveplan is now deprecated in favor of SPI_keepplan, which accomplishes the same end result with zero data copying, and no need to then spend even more cycles throwing away the original SPIPlan. The risk of long-term memory leaks while manipulating SPIPlans has also been greatly reduced. Most of this improvement is based on use of the recently-added MemoryContextSetParent primitive.
81 lines
3.2 KiB
C
81 lines
3.2 KiB
C
/*-------------------------------------------------------------------------
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*
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* spi_priv.h
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* Server Programming Interface private declarations
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*
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* Portions Copyright (c) 1996-2011, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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* src/include/executor/spi_priv.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef SPI_PRIV_H
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#define SPI_PRIV_H
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#include "executor/spi.h"
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#define _SPI_PLAN_MAGIC 569278163
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typedef struct
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{
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/* current results */
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uint32 processed; /* by Executor */
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Oid lastoid;
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SPITupleTable *tuptable;
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MemoryContext procCxt; /* procedure context */
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MemoryContext execCxt; /* executor context */
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MemoryContext savedcxt; /* context of SPI_connect's caller */
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SubTransactionId connectSubid; /* ID of connecting subtransaction */
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} _SPI_connection;
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/*
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* SPI plans have three states: saved, unsaved, or temporary.
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*
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* Ordinarily, the _SPI_plan struct itself as well as the argtypes array
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* are in a dedicated memory context identified by plancxt (which can be
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* really small). All the other subsidiary state is in plancache entries
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* identified by plancache_list (note: the list cells themselves are in
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* plancxt).
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*
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* In an unsaved plan, the plancxt as well as the plancache entries' contexts
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* are children of the SPI procedure context, so they'll all disappear at
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* function exit. plancache.c also knows that the plancache entries are
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* "unsaved", so it doesn't link them into its global list; hence they do
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* not respond to inval events. This is OK since we are presumably holding
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* adequate locks to prevent other backends from messing with the tables.
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*
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* For a saved plan, the plancxt is made a child of CacheMemoryContext
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* since it should persist until explicitly destroyed. Likewise, the
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* plancache entries will be under CacheMemoryContext since we tell
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* plancache.c to save them. We rely on plancache.c to keep the cache
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* entries up-to-date as needed in the face of invalidation events.
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*
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* There are also "temporary" SPI plans, in which the _SPI_plan struct is
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* not even palloc'd but just exists in some function's local variable.
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* The plancache entries are unsaved and exist under the SPI executor context,
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* while additional data such as argtypes and list cells is loose in the SPI
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* executor context. Such plans can be identified by having plancxt == NULL.
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*
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* Note: if the original query string contained only whitespace and comments,
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* the plancache_list will be NIL and so there is no place to store the
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* query string. We don't care about that, but we do care about the
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* argument type array, which is why it's seemingly-redundantly stored.
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*/
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typedef struct _SPI_plan
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{
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int magic; /* should equal _SPI_PLAN_MAGIC */
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bool saved; /* saved or unsaved plan? */
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List *plancache_list; /* one CachedPlanSource per parsetree */
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MemoryContext plancxt; /* Context containing _SPI_plan and data */
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int cursor_options; /* Cursor options used for planning */
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int nargs; /* number of plan arguments */
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Oid *argtypes; /* Argument types (NULL if nargs is 0) */
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ParserSetupHook parserSetup; /* alternative parameter spec method */
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void *parserSetupArg;
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} _SPI_plan;
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#endif /* SPI_PRIV_H */
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