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Generalize relation analyze in table AM interface

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Currently, there is just one algorithm for sampling tuples from a table written
in acquire_sample_rows().  Custom table AM can just redefine the way to get the
next block/tuple by implementing scan_analyze_next_block() and
scan_analyze_next_tuple() API functions.

This approach doesn't seem general enough.  For instance, it's unclear how to
sample this way index-organized tables.  This commit allows table AM to
encapsulate the whole sampling algorithm (currently implemented in
acquire_sample_rows()) into the relation_analyze() API function.

Discussion: https://postgr.es/m/CAPpHfdurb9ycV8udYqM%3Do0sPS66PJ4RCBM1g-bBpvzUfogY0EA%40mail.gmail.com
Reviewed-by: Pavel Borisov, Matthias van de Meent
This commit is contained in:
Alexander Korotkov
2024-03-30 22:34:04 +02:00
parent b154d8a6d0
commit 27bc1772fc
7 changed files with 100 additions and 125 deletions
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29
src/backend/access/heap/heapam_handler.c
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@@ -50,7 +50,6 @@ static TM_Result heapam_tuple_lock(Relation relation, ItemPointer tid,
CommandId cid, LockTupleMode mode,
LockWaitPolicy wait_policy, uint8 flags,
TM_FailureData *tmfd);
static void reform_and_rewrite_tuple(HeapTuple tuple,
Relation OldHeap, Relation NewHeap,
Datum *values, bool *isnull, RewriteState rwstate);
@@ -1052,7 +1051,15 @@ heapam_relation_copy_for_cluster(Relation OldHeap, Relation NewHeap,
pfree(isnull);
}
static bool
/*
* Prepare to analyze block `blockno` of `scan`. The scan has been started
* with SO_TYPE_ANALYZE option.
*
* This routine holds a buffer pin and lock on the heap page. They are held
* until heapam_scan_analyze_next_tuple() returns false. That is until all the
* items of the heap page are analyzed.
*/
void
heapam_scan_analyze_next_block(TableScanDesc scan, BlockNumber blockno,
BufferAccessStrategy bstrategy)
{
@@ -1072,12 +1079,19 @@ heapam_scan_analyze_next_block(TableScanDesc scan, BlockNumber blockno,
hscan->rs_cbuf = ReadBufferExtended(scan->rs_rd, MAIN_FORKNUM,
blockno, RBM_NORMAL, bstrategy);
LockBuffer(hscan->rs_cbuf, BUFFER_LOCK_SHARE);
/* in heap all blocks can contain tuples, so always return true */
return true;
}
static bool
/*
* Iterate over tuples in the block selected with
* heapam_scan_analyze_next_block(). If a tuple that's suitable for sampling
* is found, true is returned and a tuple is stored in `slot`. When no more
* tuples for sampling, false is returned and the pin and lock acquired by
* heapam_scan_analyze_next_block() are released.
*
* *liverows and *deadrows are incremented according to the encountered
* tuples.
*/
bool
heapam_scan_analyze_next_tuple(TableScanDesc scan, TransactionId OldestXmin,
double *liverows, double *deadrows,
TupleTableSlot *slot)
@@ -2637,10 +2651,9 @@ static const TableAmRoutine heapam_methods = {
.relation_copy_data = heapam_relation_copy_data,
.relation_copy_for_cluster = heapam_relation_copy_for_cluster,
.relation_vacuum = heap_vacuum_rel,
.scan_analyze_next_block = heapam_scan_analyze_next_block,
.scan_analyze_next_tuple = heapam_scan_analyze_next_tuple,
.index_build_range_scan = heapam_index_build_range_scan,
.index_validate_scan = heapam_index_validate_scan,
.relation_analyze = heapam_analyze,
.free_rd_amcache = NULL,
.relation_size = table_block_relation_size,