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Use slots more widely in tuple mapping code and make naming more consistent.

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It's inefficient to use a single slot for mapping between tuple
descriptors for multiple tuples, as previously done when using
ConvertPartitionTupleSlot(), as that means the slot's tuple descriptors
change for every tuple.

Previously we also, via ConvertPartitionTupleSlot(), built new tuples
after the mapping even in cases where we, immediately afterwards,
access individual columns again.

Refactor the code so one slot, on demand, is used for each
partition. That avoids having to change the descriptor (and allows to
use the more efficient "fixed" tuple slots). Then use slot->slot
mapping, to avoid unnecessarily forming a tuple.

As the naming between the tuple and slot mapping functions wasn't
consistent, rename them to execute_attr_map_{tuple,slot}.  It's likely
that we'll also rename convert_tuples_by_* to denote that these
functions "only" build a map, but that's left for later.

Author: Amit Khandekar and Amit Langote, editorialized by me
Reviewed-By: Amit Langote, Amit Khandekar, Andres Freund
Discussion:
    https://postgr.es/m/CAJ3gD9fR0wRNeAE8VqffNTyONS_UfFPRpqxhnD9Q42vZB+Jvpg@mail.gmail.com
    https://postgr.es/m/e4f9d743-cd4b-efb0-7574-da21d86a7f36%40lab.ntt.co.jp
Backpatch: -
This commit is contained in:
Andres Freund
2018-10-02 11:14:26 -07:00
parent 625b38ea0e
commit cc2905e963
11 changed files with 272 additions and 191 deletions
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8
src/include/access/tupconvert.h
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@@ -16,6 +16,7 @@
#include "access/htup.h"
#include "access/tupdesc.h"
#include "executor/tuptable.h"
typedef struct TupleConversionMap
@@ -41,8 +42,13 @@ extern TupleConversionMap *convert_tuples_by_name(TupleDesc indesc,
extern AttrNumber *convert_tuples_by_name_map(TupleDesc indesc,
TupleDesc outdesc,
const char *msg);
extern AttrNumber *convert_tuples_by_name_map_if_req(TupleDesc indesc,
TupleDesc outdesc,
const char *msg);
extern HeapTuple do_convert_tuple(HeapTuple tuple, TupleConversionMap *map);
extern HeapTuple execute_attr_map_tuple(HeapTuple tuple, TupleConversionMap *map);
extern TupleTableSlot *execute_attr_map_slot(AttrNumber *attrMap,
TupleTableSlot *in_slot, TupleTableSlot *out_slot);
extern void free_conversion_map(TupleConversionMap *map);