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65c5fcd353
This patch reduces pg_am to just two columns, a name and a handler function. All the data formerly obtained from pg_am is now provided in a C struct returned by the handler function. This is similar to the designs we've adopted for FDWs and tablesample methods. There are multiple advantages. For one, the index AM's support functions are now simple C functions, making them faster to call and much less error-prone, since the C compiler can now check function signatures. For another, this will make it far more practical to define index access methods in installable extensions. A disadvantage is that SQL-level code can no longer see attributes of index AMs; in particular, some of the crosschecks in the opr_sanity regression test are no longer possible from SQL. We've addressed that by adding a facility for the index AM to perform such checks instead. (Much more could be done in that line, but for now we're content if the amvalidate functions more or less replace what opr_sanity used to do.) We might also want to expose some sort of reporting functionality, but this patch doesn't do that. Alexander Korotkov, reviewed by Petr Jelínek, and rather heavily editorialized on by me.
175 lines
5.3 KiB
C
175 lines
5.3 KiB
C
/*-------------------------------------------------------------------------
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*
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* amapi.h
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* API for Postgres index access methods.
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*
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* Copyright (c) 2015-2016, PostgreSQL Global Development Group
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*
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* src/include/access/amapi.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef AMAPI_H
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#define AMAPI_H
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#include "access/genam.h"
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/*
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* We don't wish to include planner header files here, since most of an index
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* AM's implementation isn't concerned with those data structures. To allow
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* declaring amcostestimate_function here, use forward struct references.
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*/
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struct PlannerInfo;
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struct IndexPath;
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/* Likewise, this file shouldn't depend on execnodes.h. */
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struct IndexInfo;
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/*
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* Callback function signatures --- see indexam.sgml for more info.
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*/
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/* build new index */
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typedef IndexBuildResult *(*ambuild_function) (Relation heapRelation,
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Relation indexRelation,
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struct IndexInfo *indexInfo);
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/* build empty index */
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typedef void (*ambuildempty_function) (Relation indexRelation);
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/* insert this tuple */
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typedef bool (*aminsert_function) (Relation indexRelation,
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Datum *values,
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bool *isnull,
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ItemPointer heap_tid,
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Relation heapRelation,
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IndexUniqueCheck checkUnique);
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/* bulk delete */
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typedef IndexBulkDeleteResult *(*ambulkdelete_function) (IndexVacuumInfo *info,
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IndexBulkDeleteResult *stats,
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IndexBulkDeleteCallback callback,
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void *callback_state);
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/* post-VACUUM cleanup */
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typedef IndexBulkDeleteResult *(*amvacuumcleanup_function) (IndexVacuumInfo *info,
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IndexBulkDeleteResult *stats);
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/* can indexscan return IndexTuples? */
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typedef bool (*amcanreturn_function) (Relation indexRelation, int attno);
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/* estimate cost of an indexscan */
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typedef void (*amcostestimate_function) (struct PlannerInfo *root,
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struct IndexPath *path,
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double loop_count,
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Cost *indexStartupCost,
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Cost *indexTotalCost,
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Selectivity *indexSelectivity,
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double *indexCorrelation);
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/* parse index reloptions */
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typedef bytea *(*amoptions_function) (Datum reloptions,
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bool validate);
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/* validate definition of an opclass for this AM */
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typedef bool (*amvalidate_function) (Oid opclassoid);
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/* prepare for index scan */
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typedef IndexScanDesc (*ambeginscan_function) (Relation indexRelation,
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int nkeys,
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int norderbys);
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/* (re)start index scan */
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typedef void (*amrescan_function) (IndexScanDesc scan,
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ScanKey keys,
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int nkeys,
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ScanKey orderbys,
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int norderbys);
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/* next valid tuple */
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typedef bool (*amgettuple_function) (IndexScanDesc scan,
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ScanDirection direction);
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/* fetch all valid tuples */
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typedef int64 (*amgetbitmap_function) (IndexScanDesc scan,
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TIDBitmap *tbm);
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/* end index scan */
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typedef void (*amendscan_function) (IndexScanDesc scan);
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/* mark current scan position */
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typedef void (*ammarkpos_function) (IndexScanDesc scan);
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/* restore marked scan position */
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typedef void (*amrestrpos_function) (IndexScanDesc scan);
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/*
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* API struct for an index AM. Note this must be stored in a single palloc'd
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* chunk of memory.
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*/
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typedef struct IndexAmRoutine
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{
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NodeTag type;
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/*
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* Total number of strategies (operators) by which we can traverse/search
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* this AM. Zero if AM does not have a fixed set of strategy assignments.
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*/
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uint16 amstrategies;
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/* total number of support functions that this AM uses */
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uint16 amsupport;
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/* does AM support ORDER BY indexed column's value? */
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bool amcanorder;
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/* does AM support ORDER BY result of an operator on indexed column? */
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bool amcanorderbyop;
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/* does AM support backward scanning? */
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bool amcanbackward;
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/* does AM support UNIQUE indexes? */
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bool amcanunique;
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/* does AM support multi-column indexes? */
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bool amcanmulticol;
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/* does AM require scans to have a constraint on the first index column? */
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bool amoptionalkey;
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/* does AM handle ScalarArrayOpExpr quals? */
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bool amsearcharray;
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/* does AM handle IS NULL/IS NOT NULL quals? */
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bool amsearchnulls;
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/* can index storage data type differ from column data type? */
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bool amstorage;
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/* can an index of this type be clustered on? */
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bool amclusterable;
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/* does AM handle predicate locks? */
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bool ampredlocks;
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/* type of data stored in index, or InvalidOid if variable */
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Oid amkeytype;
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/* interface functions */
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ambuild_function ambuild;
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ambuildempty_function ambuildempty;
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aminsert_function aminsert;
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ambulkdelete_function ambulkdelete;
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amvacuumcleanup_function amvacuumcleanup;
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amcanreturn_function amcanreturn; /* can be NULL */
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amcostestimate_function amcostestimate;
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amoptions_function amoptions;
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amvalidate_function amvalidate;
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ambeginscan_function ambeginscan;
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amrescan_function amrescan;
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amgettuple_function amgettuple; /* can be NULL */
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amgetbitmap_function amgetbitmap; /* can be NULL */
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amendscan_function amendscan;
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ammarkpos_function ammarkpos; /* can be NULL */
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amrestrpos_function amrestrpos; /* can be NULL */
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} IndexAmRoutine;
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/* Functions in access/index/amapi.c */
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extern IndexAmRoutine *GetIndexAmRoutine(Oid amhandler);
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extern IndexAmRoutine *GetIndexAmRoutineByAmId(Oid amoid);
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extern Datum amvalidate(PG_FUNCTION_ARGS);
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#endif /* AMAPI_H */
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