src/include/commands/vacuum.h

/*-------------------------------------------------------------------------
 *
 * vacuum.h
 *	  header file for postgres vacuum cleaner and statistics analyzer
 *
 *
 * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * $PostgreSQL: pgsql/src/include/commands/vacuum.h,v 1.68 2006/11/05 22:42:10 tgl Exp $
 *
 *-------------------------------------------------------------------------
 */
#ifndef VACUUM_H
#define VACUUM_H

#include "access/htup.h"
#include "catalog/pg_statistic.h"
#include "catalog/pg_type.h"
#include "nodes/parsenodes.h"
#include "storage/lock.h"
#include "utils/rel.h"

/*----------
 * ANALYZE builds one of these structs for each attribute (column) that is
 * to be analyzed.	The struct and subsidiary data are in anl_context,
 * so they live until the end of the ANALYZE operation.
 *
 * The type-specific typanalyze function is passed a pointer to this struct
 * and must return TRUE to continue analysis, FALSE to skip analysis of this
 * column.	In the TRUE case it must set the compute_stats and minrows fields,
 * and can optionally set extra_data to pass additional info to compute_stats.
 * minrows is its request for the minimum number of sample rows to be gathered
 * (but note this request might not be honored, eg if there are fewer rows
 * than that in the table).
 *
 * The compute_stats routine will be called after sample rows have been
 * gathered.  Aside from this struct, it is passed:
 *		fetchfunc: a function for accessing the column values from the
 *				   sample rows
 *		samplerows: the number of sample tuples
 *		totalrows: estimated total number of rows in relation
 * The fetchfunc may be called with rownum running from 0 to samplerows-1.
 * It returns a Datum and an isNull flag.
 *
 * compute_stats should set stats_valid TRUE if it is able to compute
 * any useful statistics.  If it does, the remainder of the struct holds
 * the information to be stored in a pg_statistic row for the column.  Be
 * careful to allocate any pointed-to data in anl_context, which will NOT
 * be CurrentMemoryContext when compute_stats is called.
 *----------
 */
typedef struct VacAttrStats *VacAttrStatsP;

typedef Datum (*AnalyzeAttrFetchFunc) (VacAttrStatsP stats, int rownum,
												   bool *isNull);

typedef struct PgStatistic
{
	bool		stats_valid;
	float4		stanullfrac;	/* fraction of entries that are NULL */
	int4		stawidth;		/* average width of column values */
	float4		stadistinct;	/* # distinct values */
	int2		stakind[STATISTIC_NUM_SLOTS];
	Oid			staop[STATISTIC_NUM_SLOTS];
	int			numnumbers[STATISTIC_NUM_SLOTS];
	float4	   *stanumbers[STATISTIC_NUM_SLOTS];
	int			numvalues[STATISTIC_NUM_SLOTS];
	Datum	   *stavalues[STATISTIC_NUM_SLOTS];
	
} PgStatistic;

typedef struct VacAttrStats
{
	/*
	 * These fields are set up by the main ANALYZE code before invoking the
	 * type-specific typanalyze function.
	 */
	Form_pg_attribute attr;		/* copy of pg_attribute row for column */
	Form_pg_type attrtype;		/* copy of pg_type row for column */
	MemoryContext anl_context;	/* where to save long-lived data */

	/*
	 * These fields must be filled in by the typanalyze routine, unless it
	 * returns FALSE.
	 */
	void		(*compute_stats) (VacAttrStatsP stats,
											  AnalyzeAttrFetchFunc fetchfunc,
											  int samplerows,
											  double totalrows);
	int			minrows;		/* Minimum # of rows wanted for stats */
	void	   *extra_data;		/* for extra type-specific data */

	/*
	 * These fields are to be filled in by the compute_stats routine. (They
	 * are initialized to zero when the struct is created.)
	 */
	PgStatistic pgstat;
	
	/*
	 * These fields are private to the main ANALYZE code and should not be
	 * looked at by type-specific functions.
	 */
	int			tupattnum;		/* attribute number within tuples */
	HeapTuple  *rows;			/* access info for std fetch function */
	TupleDesc	tupDesc;
	Datum	   *exprvals;		/* access info for index fetch function */
	bool	   *exprnulls;
	int			rowstride;
} VacAttrStats;

/*
 * The "vtlinks" array keeps information about each recently-updated tuple
 * ("recent" meaning its XMAX is too new to let us recycle the tuple).
 * We store the tuple's own TID as well as its t_ctid (its link to the next
 * newer tuple version).  Searching in this array allows us to follow update
 * chains backwards from newer to older tuples.  When we move a member of an
 * update chain, we must move *all* the live members of the chain, so that we
 * can maintain their t_ctid link relationships (we must not just overwrite
 * t_ctid in an existing tuple).
 *
 * Note: because t_ctid links can be stale (this would only occur if a prior
 * VACUUM crashed partway through), it is possible that new_tid points to an
 * empty slot or unrelated tuple.  We have to check the linkage as we follow
 * it, just as is done in EvalPlanQual.
 */
typedef struct VTupleLinkData
{
	ItemPointerData new_tid;	/* t_ctid of an updated tuple */
	ItemPointerData this_tid;	/* t_self of the tuple */
} VTupleLinkData;

typedef VTupleLinkData *VTupleLink;

/*
 * VRelStats contains the data acquired by scan_heap for use later
 */
typedef struct VRelStats
{
	/* miscellaneous statistics */
	BlockNumber rel_pages;
	double		rel_tuples;
	Size		min_tlen;
	Size		max_tlen;
	bool		hasindex;
	/* vtlinks array for tuple chain following - sorted by new_tid */
	int			num_vtlinks;
	VTupleLink	vtlinks;
} VRelStats;

/* GUC parameters */
extern PGDLLIMPORT int default_statistics_target; /* PGDLLIMPORT for PostGIS */
extern PGDLLIMPORT double analyze_relative_error;
extern int	vacuum_freeze_min_age;


/* in commands/vacuum.c */
extern void vacuum(VacuumStmt *vacstmt, List *relids, int preferred_seg_num);
extern void vac_open_indexes(Relation relation, LOCKMODE lockmode,
				 int *nindexes, Relation **Irel);
extern void vac_close_indexes(int nindexes, Relation *Irel, LOCKMODE lockmode);
extern void vac_update_relstats(Relation rel,
								BlockNumber num_pages,
								double num_tuples,
								bool hasindex,
								TransactionId frozenxid,
								List *updated_stats);
extern void vacuum_set_xid_limits(VacuumStmt *vacstmt, bool sharedRel,
					  TransactionId *oldestXmin,
					  TransactionId *freezeLimit);
extern void vac_update_datfrozenxid(void);
extern bool vac_is_partial_index(Relation indrel);
extern void vacuum_delay_point(void);

/* in commands/vacuumlazy.c */
extern void lazy_vacuum_rel(Relation onerel, VacuumStmt *vacstmt, List *updated_stats);
extern void vacuum_appendonly_rel(Relation aorel, void *vacrelstats, bool isVacFull);
extern void vacuum_parquet_rel(Relation parquetrel, void *vacrelstats, bool isVacFull);
extern void gen_oids_for_bitmaps(VacuumStmt *vacstmt, Relation onerel);
extern List *get_oids_for_bitmap(List *all_extra_oids, Relation Irel, Relation onerel, int occurrence);

/* in commands/analyze.c */
extern void analyzeStatement(VacuumStmt *vacstmt, List *relids, int preferred_seg_num);
extern void analyzeStmt(VacuumStmt *vacstmt, List *relids, int target_seg_num);
#endif   /* VACUUM_H */