diff options
Diffstat (limited to 'src/include/executor')
| -rw-r--r-- | src/include/executor/spi.h | 1 | ||||
| -rw-r--r-- | src/include/executor/spi_priv.h | 41 |
2 files changed, 24 insertions, 18 deletions
diff --git a/src/include/executor/spi.h b/src/include/executor/spi.h index 7199debb27a..3b1b27ee49e 100644 --- a/src/include/executor/spi.h +++ b/src/include/executor/spi.h @@ -93,6 +93,7 @@ extern SPIPlanPtr SPI_prepare_params(const char *src, ParserSetupHook parserSetup, void *parserSetupArg, int cursorOptions); +extern int SPI_keepplan(SPIPlanPtr plan); extern SPIPlanPtr SPI_saveplan(SPIPlanPtr plan); extern int SPI_freeplan(SPIPlanPtr plan); diff --git a/src/include/executor/spi_priv.h b/src/include/executor/spi_priv.h index 5865f532802..3e7bf860948 100644 --- a/src/include/executor/spi_priv.h +++ b/src/include/executor/spi_priv.h @@ -32,27 +32,32 @@ typedef struct } _SPI_connection; /* - * SPI plans have two states: saved or unsaved. + * SPI plans have three states: saved, unsaved, or temporary. * - * For an unsaved plan, the _SPI_plan struct and all its subsidiary data are in - * a dedicated memory context identified by plancxt. An unsaved plan is good - * at most for the current transaction, since the locks that protect it from - * schema changes will be lost at end of transaction. Hence the plancxt is - * always a transient one. + * 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). * - * For a saved plan, the _SPI_plan struct and the argument type array are in - * the 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). We rely on plancache.c to keep the cache - * entries up-to-date as needed. The plancxt is a child of CacheMemoryContext - * since it should persist until explicitly destroyed. + * 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. * - * To avoid redundant coding, the representation of unsaved plans matches - * that of saved plans, ie, plancache_list is a list of CachedPlanSource - * structs which in turn point to CachedPlan structs. However, in an unsaved - * plan all these structs are just created by spi.c and are not known to - * plancache.c. We don't try very hard to make all their fields valid, - * only the ones spi.c actually uses. + * 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. * * 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 |