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Add TID Range Scans to support efficient scanning ranges of TIDs

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This adds a new executor node named TID Range Scan.  The query planner
will generate paths for TID Range scans when quals are discovered on base
relations which search for ranges on the table's ctid column.  These
ranges may be open at either end. For example, WHERE ctid >= '(10,0)';
will return all tuples on page 10 and over.

To support this, two new optional callback functions have been added to
table AM.  scan_set_tidrange is used to set the scan range to just the
given range of TIDs.  scan_getnextslot_tidrange fetches the next tuple
in the given range.

For AMs were scanning ranges of TIDs would not make sense, these functions
can be set to NULL in the TableAmRoutine.  The query planner won't
generate TID Range Scan Paths in that case.

Author: Edmund Horner, David Rowley
Reviewed-by: David Rowley, Tomas Vondra, Tom Lane, Andres Freund, Zhihong Yu
Discussion: https://postgr.es/m/CAMyN-kB-nFTkF=VA_JPwFNo08S0d-Yk0F741S2B7LDmYAi8eyA@mail.gmail.com
This commit is contained in:
David Rowley
2021-02-27 22:59:36 +13:00
parent f4adc41c4f
commit bb437f995d
36 changed files with 1654 additions and 22 deletions
Download Patch File Download Diff File Expand all files Collapse all files

6
src/include/access/heapam.h
View File

@@ -121,7 +121,11 @@ extern void heap_endscan(TableScanDesc scan);
extern HeapTuple heap_getnext(TableScanDesc scan, ScanDirection direction);
extern bool heap_getnextslot(TableScanDesc sscan,
ScanDirection direction, struct TupleTableSlot *slot);
extern void heap_set_tidrange(TableScanDesc sscan, ItemPointer mintid,
ItemPointer maxtid);
extern bool heap_getnextslot_tidrange(TableScanDesc sscan,
ScanDirection direction,
TupleTableSlot *slot);
extern bool heap_fetch(Relation relation, Snapshot snapshot,
HeapTuple tuple, Buffer *userbuf);
extern bool heap_hot_search_buffer(ItemPointer tid, Relation relation,

4
src/include/access/relscan.h
View File

@@ -36,6 +36,10 @@ typedef struct TableScanDescData
int rs_nkeys; /* number of scan keys */
struct ScanKeyData *rs_key; /* array of scan key descriptors */
/* Range of ItemPointers for table_scan_getnextslot_tidrange() to scan. */
ItemPointerData rs_mintid;
ItemPointerData rs_maxtid;
/*
* Information about type and behaviour of the scan, a bitmask of members
* of the ScanOptions enum (see tableam.h).

97
src/include/access/tableam.h
View File

@@ -49,18 +49,19 @@ typedef enum ScanOptions
SO_TYPE_BITMAPSCAN = 1 << 1,
SO_TYPE_SAMPLESCAN = 1 << 2,
SO_TYPE_TIDSCAN = 1 << 3,
SO_TYPE_ANALYZE = 1 << 4,
SO_TYPE_TIDRANGESCAN = 1 << 4,
SO_TYPE_ANALYZE = 1 << 5,
/* several of SO_ALLOW_* may be specified */
/* allow or disallow use of access strategy */
SO_ALLOW_STRAT = 1 << 5,
SO_ALLOW_STRAT = 1 << 6,
/* report location to syncscan logic? */
SO_ALLOW_SYNC = 1 << 6,
SO_ALLOW_SYNC = 1 << 7,
/* verify visibility page-at-a-time? */
SO_ALLOW_PAGEMODE = 1 << 7,
SO_ALLOW_PAGEMODE = 1 << 8,
/* unregister snapshot at scan end? */
SO_TEMP_SNAPSHOT = 1 << 8
SO_TEMP_SNAPSHOT = 1 << 9
} ScanOptions;
/*
@@ -325,6 +326,34 @@ typedef struct TableAmRoutine
ScanDirection direction,
TupleTableSlot *slot);
/*-----------
* Optional functions to provide scanning for ranges of ItemPointers.
* Implementations must either provide both of these functions, or neither
* of them.
*
* Implementations of scan_set_tidrange must themselves handle
* ItemPointers of any value. i.e, they must handle each of the following:
*
* 1) mintid or maxtid is beyond the end of the table; and
* 2) mintid is above maxtid; and
* 3) item offset for mintid or maxtid is beyond the maximum offset
* allowed by the AM.
*
* Implementations can assume that scan_set_tidrange is always called
* before can_getnextslot_tidrange or after scan_rescan and before any
* further calls to scan_getnextslot_tidrange.
*/
void (*scan_set_tidrange) (TableScanDesc scan,
ItemPointer mintid,
ItemPointer maxtid);
/*
* Return next tuple from `scan` that's in the range of TIDs defined by
* scan_set_tidrange.
*/
bool (*scan_getnextslot_tidrange) (TableScanDesc scan,
ScanDirection direction,
TupleTableSlot *slot);
/* ------------------------------------------------------------------------
* Parallel table scan related functions.
@@ -1015,6 +1044,64 @@ table_scan_getnextslot(TableScanDesc sscan, ScanDirection direction, TupleTableS
return sscan->rs_rd->rd_tableam->scan_getnextslot(sscan, direction, slot);
}
/* ----------------------------------------------------------------------------
* TID Range scanning related functions.
* ----------------------------------------------------------------------------
*/
/*
* table_beginscan_tidrange is the entry point for setting up a TableScanDesc
* for a TID range scan.
*/
static inline TableScanDesc
table_beginscan_tidrange(Relation rel, Snapshot snapshot,
ItemPointer mintid,
ItemPointer maxtid)
{
TableScanDesc sscan;
uint32 flags = SO_TYPE_TIDRANGESCAN | SO_ALLOW_PAGEMODE;
sscan = rel->rd_tableam->scan_begin(rel, snapshot, 0, NULL, NULL, flags);
/* Set the range of TIDs to scan */
sscan->rs_rd->rd_tableam->scan_set_tidrange(sscan, mintid, maxtid);
return sscan;
}
/*
* table_rescan_tidrange resets the scan position and sets the minimum and
* maximum TID range to scan for a TableScanDesc created by
* table_beginscan_tidrange.
*/
static inline void
table_rescan_tidrange(TableScanDesc sscan, ItemPointer mintid,
ItemPointer maxtid)
{
/* Ensure table_beginscan_tidrange() was used. */
Assert((sscan->rs_flags & SO_TYPE_TIDRANGESCAN) != 0);
sscan->rs_rd->rd_tableam->scan_rescan(sscan, NULL, false, false, false, false);
sscan->rs_rd->rd_tableam->scan_set_tidrange(sscan, mintid, maxtid);
}
/*
* Fetch the next tuple from `sscan` for a TID range scan created by
* table_beginscan_tidrange(). Stores the tuple in `slot` and returns true,
* or returns false if no more tuples exist in the range.
*/
static inline bool
table_scan_getnextslot_tidrange(TableScanDesc sscan, ScanDirection direction,
TupleTableSlot *slot)
{
/* Ensure table_beginscan_tidrange() was used. */
Assert((sscan->rs_flags & SO_TYPE_TIDRANGESCAN) != 0);
return sscan->rs_rd->rd_tableam->scan_getnextslot_tidrange(sscan,
direction,
slot);
}
/* ----------------------------------------------------------------------------
* Parallel table scan related functions.