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https://issues.apache.org/jira/browse/SPARK-59557?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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David Mollitor updated SPARK-59557:
-----------------------------------
Description:
h2. Summary
Casting an integral (byte/short/int/long) or boolean value to string currently
routes through {{{}java.lang.String{}}}, allocating several throwaway objects
per row. Both the interpreted and codegen cast paths in {{ToStringBase}} emit
{{UTF8String.fromString(String.valueOf(x))}} (codegen) /
{{UTF8String.fromString(x.toString)}} (interpreted).
{{UTF8String.fromString(String)}} then does
{{{}str.getBytes(StandardCharsets.UTF_8){}}}, so a single \{{CAST(<long> AS
STRING) }}allocates:
* a {{java.lang.String}} (from {{{}Long.toString{}}}),
* that String's backing {{{}byte[]{}}},
* a re-encoded UTF-8 {{byte[]}} (from {{{}getBytes{}}}), and
* the result {{{}UTF8String{}}}.
Only the last two are essential. {{CAST(<integral> AS STRING)}} is a very common
expression (key building, string concatenation, display), so the redundant
{{java.lang.String}} round-trip is broad, avoidable per-row overhead.
was:
h2. Summary
Casting an integral (byte/short/int/long) or boolean value to string currently
routes through {{{}java.lang.String{}}}, allocating several throwaway objects
per row.
Both the interpreted and codegen cast paths in {{ToStringBase}} emit
{{UTF8String.fromString(String.valueOf(x))}} (codegen) /
\{{UTF8String.fromString(x.toString)}} (interpreted).
{{UTF8String.fromString(String)}} then does
{{{}str.getBytes(StandardCharsets.UTF_8){}}}, so a single {{CAST(<long> AS
STRING) }}allocates:
* a {{java.lang.String}} (from {{{}Long.toString{}}}),
* that String's backing {{{}byte[]{}}},
* a re-encoded UTF-8 {{byte[]}} (from {{{}getBytes{}}}), and
* the result {{{}UTF8String{}}}.
Only the last two are essential. {{CAST(<integral> AS STRING)}} is a very common
expression (key building, string concatenation, display), so the redundant
{{java.lang.String}} round-trip is broad, avoidable per-row overhead.
> Avoid intermediate java.lang.String when casting integral and boolean values
> to string
> --------------------------------------------------------------------------------------
>
> Key: SPARK-59557
> URL: https://issues.apache.org/jira/browse/SPARK-59557
> Project: Spark
> Issue Type: Improvement
> Components: SQL
> Affects Versions: 4.1.0
> Reporter: David Mollitor
> Priority: Minor
>
> h2. Summary
> Casting an integral (byte/short/int/long) or boolean value to string
> currently routes through {{{}java.lang.String{}}}, allocating several
> throwaway objects per row. Both the interpreted and codegen cast paths in
> {{ToStringBase}} emit {{UTF8String.fromString(String.valueOf(x))}} (codegen)
> / {{UTF8String.fromString(x.toString)}} (interpreted).
> {{UTF8String.fromString(String)}} then does
> {{{}str.getBytes(StandardCharsets.UTF_8){}}}, so a single \{{CAST(<long> AS
> STRING) }}allocates:
> * a {{java.lang.String}} (from {{{}Long.toString{}}}),
> * that String's backing {{{}byte[]{}}},
> * a re-encoded UTF-8 {{byte[]}} (from {{{}getBytes{}}}), and
> * the result {{{}UTF8String{}}}.
> Only the last two are essential. {{CAST(<integral> AS STRING)}} is a very
> common
> expression (key building, string concatenation, display), so the redundant
> {{java.lang.String}} round-trip is broad, avoidable per-row overhead.
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