Paul Rogers created DRILL-5759:
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Summary: Performance hit: JSON reader causes repeated vector
reallocations
Key: DRILL-5759
URL: https://issues.apache.org/jira/browse/DRILL-5759
Project: Apache Drill
Issue Type: Improvement
Affects Versions: 1.10.0
Reporter: Paul Rogers
Priority: Minor
Run the query in DRILL-5753 with DEBUG level logging. This query uses the JSON
record reader. You will see many messages about vector reallocation. These
messages show that the JSON reader incorrectly allocated vector sizes.
The specific problem is with repeated types. In the messages, note that vectors
start off with 4096 values, which is the target row count. But, the data
contains repeated columns, and so the vectors must grow multiple times to hold
the repeated items. On the first batch, heuristics might be used to guess the
cardinality. On the second and subsequent batches, empirical data gathered on
the first batch could be used to better allocate the subsequent batches.
The result is memory thrashing and a performance hit as memory is allocated,
copied and released multiple times.
{code}
BigIntVector - Reallocating vector [$data$(BIGINT:REQUIRED)]. # of bytes:
[32768] -> [65536]
UInt4Vector - Reallocating vector [$offsets$(UINT4:REQUIRED)]. # of bytes:
[16384] -> [32768]
UInt4Vector - Reallocating vector [$offsets$(UINT4:REQUIRED)]. # of bytes:
[16384] -> [32768]
UInt1Vector - Reallocating vector [$bits$(UINT1:REQUIRED)]. # of bytes: [4096]
-> [8192]
UInt1Vector - Reallocating vector [$bits$(UINT1:REQUIRED)]. # of bytes: [4096]
-> [8192]
UInt1Vector - Reallocating vector [$bits$(UINT1:REQUIRED)]. # of bytes: [4096]
-> [8192]
BigIntVector - Reallocating vector [c(BIGINT:OPTIONAL)]. # of bytes: [32768] ->
[65536]
UInt1Vector - Reallocating vector [$bits$(UINT1:REQUIRED)]. # of bytes: [4096]
-> [8192]
Float8Vector - Reallocating vector [d(FLOAT8:OPTIONAL)]. # of bytes: [32768] ->
[65536]
BigIntVector - Reallocating vector [$data$(BIGINT:REQUIRED)]. # of bytes:
[65536] -> [131072]
UInt4Vector - Reallocating vector [$offsets$(UINT4:REQUIRED)]. # of bytes:
[32768] -> [65536]
UInt4Vector - Reallocating vector [$offsets$(UINT4:REQUIRED)]. # of bytes:
[32768] -> [65536]
UInt1Vector - Reallocating vector [$bits$(UINT1:REQUIRED)]. # of bytes: [8192]
-> [16384]
UInt1Vector - Reallocating vector [$bits$(UINT1:REQUIRED)]. # of bytes: [8192]
-> [16384]
BigIntVector - Reallocating vector [c(BIGINT:OPTIONAL)]. # of bytes: [65536] ->
[131072]
UInt1Vector - Reallocating vector [$bits$(UINT1:REQUIRED)]. # of bytes: [8192]
-> [16384]
Float8Vector - Reallocating vector [d(FLOAT8:OPTIONAL)]. # of bytes: [65536] ->
[131072]
UInt1Vector - Reallocating vector [$bits$(UINT1:REQUIRED)]. # of bytes: [8192]
-> [16384]
UInt4Vector - Reallocating vector [$offsets$(UINT4:REQUIRED)]. # of bytes:
[16384] -> [32768]
UInt4Vector - Reallocating vector [$offsets$(UINT4:REQUIRED)]. # of bytes:
[16384] -> [32768]
UInt4Vector - Reallocating vector [$offsets$(UINT4:REQUIRED)]. # of bytes:
[16384] -> [32768]
UInt1Vector - Reallocating vector [$bits$(UINT1:REQUIRED)]. # of bytes: [4096]
-> [8192]
UInt1Vector - Reallocating vector [$bits$(UINT1:REQUIRED)]. # of bytes: [4096]
-> [8192]
BigIntVector - Reallocating vector [col1(BIGINT:OPTIONAL)]. # of bytes: [32768]
-> [65536]
BigIntVector - Reallocating vector [$data$(BIGINT:REQUIRED)]. # of bytes:
[131072] -> [262144]
UInt4Vector - Reallocating vector [$offsets$(UINT4:REQUIRED)]. # of bytes:
[65536] -> [131072]
UInt1Vector - Reallocating vector [$bits$(UINT1:REQUIRED)]. # of bytes: [16384]
-> [32768]
Float8Vector - Reallocating vector [d(FLOAT8:OPTIONAL)]. # of bytes: [131072]
-> [262144]
UInt1Vector - Reallocating vector [$bits$(UINT1:REQUIRED)]. # of bytes: [16384]
-> [32768]
UInt4Vector - Reallocating vector [$offsets$(UINT4:REQUIRED)]. # of bytes:
[65536] -> [131072]
UInt1Vector - Reallocating vector [$bits$(UINT1:REQUIRED)]. # of bytes: [16384]
-> [32768]
UInt1Vector - Reallocating vector [$bits$(UINT1:REQUIRED)]. # of bytes: [16384]
-> [32768]
BigIntVector - Reallocating vector [c(BIGINT:OPTIONAL)]. # of bytes: [131072]
-> [262144]
UInt4Vector - Reallocating vector [$offsets$(UINT4:REQUIRED)]. # of bytes:
[16384] -> [32768]
UInt4Vector - Reallocating vector [$offsets$(UINT4:REQUIRED)]. # of bytes:
[16384] -> [32768]
UInt4Vector - Reallocating vector [$offsets$(UINT4:REQUIRED)]. # of bytes:
[32768] -> [65536]
UInt4Vector - Reallocating vector [$offsets$(UINT4:REQUIRED)]. # of bytes:
[32768] -> [65536]
UInt4Vector - Reallocating vector [$offsets$(UINT4:REQUIRED)]. # of bytes:
[32768] -> [65536]
UInt4Vector - Reallocating vector [$offsets$(UINT4:REQUIRED)]. # of bytes:
[16384] -> [32768]
{code}
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