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Look up compressed column metadata only at planning time

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Now we look them up again at execution time, which adds up for tables
with a large number of chunks.

This gives about 15% speedup (100 mcs) on a small query on a table from
tests with 50 chunks:
`select id, ts, value from metric_compressed order by id, ts limit 100;`
This commit is contained in:
Alexander Kuzmenkov 2023-04-06 18:10:15 +04:00
parent df70f3e050
commit 8c77be6c68
3 changed files with 24 additions and 10 deletions
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11
tsl/src/nodes/decompress_chunk/decompress_chunk.h
View File

@ -49,6 +49,17 @@ typedef struct DecompressChunkPath
* uncompressed chunk, but are still used for decompression.
*/
List *decompression_map;
/*
* This Int list is parallel to the compressed scan targetlist, just like
* the above one. The value is true if a given targetlist entry is a
* segmentby column, false otherwise. Has the same length as the above list.
* We have to use the parallel lists and not a list of structs, because the
* Plans have to be copyable by the Postgres _copy functions, and we can't
* do that for a custom struct.
*/
List *is_segmentby_column;
List *compressed_pathkeys;
bool needs_sequence_num;
bool reverse;

17
tsl/src/nodes/decompress_chunk/exec.c
View File

@ -71,6 +71,7 @@ typedef struct DecompressChunkState
{
CustomScanState csstate;
List *decompression_map;
List *is_segmentby_column;
int num_columns;
DecompressChunkColumnState *columns;
@ -112,6 +113,7 @@ decompress_chunk_state_create(CustomScan *cscan)
state->chunk_relid = lsecond_int(settings);
state->reverse = lthird_int(settings);
state->decompression_map = lsecond(cscan->custom_private);
state->is_segmentby_column = lthird(cscan->custom_private);
return (Node *) state;
}
@ -128,7 +130,6 @@ initialize_column_state(DecompressChunkState *state)
{
ScanState *ss = (ScanState *) state;
TupleDesc desc = ss->ss_ScanTupleSlot->tts_tupleDescriptor;
ListCell *lc;
if (list_length(state->decompression_map) == 0)
{
@ -140,11 +141,14 @@ initialize_column_state(DecompressChunkState *state)
AttrNumber next_compressed_scan_attno = 0;
state->num_columns = 0;
foreach (lc, state->decompression_map)
ListCell *dest_cell;
ListCell *is_segmentby_cell;
Assert(list_length(state->decompression_map) == list_length(state->is_segmentby_column));
forboth (dest_cell, state->decompression_map, is_segmentby_cell, state->is_segmentby_column)
{
next_compressed_scan_attno++;
AttrNumber output_attno = lfirst_int(lc);
AttrNumber output_attno = lfirst_int(dest_cell);
if (output_attno == 0)
{
/* We are asked not to decompress this column, skip it. */
@ -162,13 +166,10 @@ initialize_column_state(DecompressChunkState *state)
/* normal column that is also present in uncompressed chunk */
Form_pg_attribute attribute =
TupleDescAttr(desc, AttrNumberGetAttrOffset(output_attno));
FormData_hypertable_compression *ht_info =
get_column_compressioninfo(state->hypertable_compression_info,
NameStr(attribute->attname));
column->typid = attribute->atttypid;
if (ht_info->segmentby_column_index > 0)
if (lfirst_int(is_segmentby_cell))
column->type = SEGMENTBY_COLUMN;
else
column->type = COMPRESSED_COLUMN;
@ -290,8 +291,6 @@ decompress_chunk_begin(CustomScanState *node, EState *estate, int eflags)
}
}
state->hypertable_compression_info = ts_hypertable_compression_get(state->hypertable_id);
initialize_column_state(state);
node->custom_ps = lappend(node->custom_ps, ExecInitNode(compressed_scan, estate, eflags));

6
tsl/src/nodes/decompress_chunk/planner.c
View File

@ -227,6 +227,9 @@ build_decompression_map(DecompressChunkPath *path, List *scan_tlist, Bitmapset *
path->decompression_map =
lappend_int(path->decompression_map, destination_attno_in_uncompressed_chunk);
path->is_segmentby_column =
lappend_int(path->is_segmentby_column,
compression_info && compression_info->segmentby_column_index != 0);
}
/*
@ -472,7 +475,8 @@ decompress_chunk_plan_create(PlannerInfo *root, RelOptInfo *rel, CustomPath *pat
settings = list_make3_int(dcpath->info->hypertable_id,
dcpath->info->chunk_rte->relid,
dcpath->reverse);
decompress_plan->custom_private = list_make2(settings, dcpath->decompression_map);
decompress_plan->custom_private =
list_make3(settings, dcpath->decompression_map, dcpath->is_segmentby_column);
return &decompress_plan->scan.plan;
}