[
https://issues.apache.org/jira/browse/CALCITE-7174?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Alessandro Solimando updated CALCITE-7174:
------------------------------------------
Description:
[RexUtil.java#isLossLessCast|https://github.com/apache/calcite/blob/calcite-1.40.0/core/src/main/java/org/apache/calcite/rex/RexUtil.java#L1692]
doesn't handle casts from the INT family to non-INT numeric are not covered at
all and always considered lossy.
This ticket proposes to detect the following additional cases as being lossless:
- INTEGER-family (signed and unsigned) => INTEGER-family when the target range
fully covers the source range, checked via numeric limits
- DECIMAL(p, s=0) => INTEGER-family when the decimal range is entirely
contained in the target integer range
- INTEGER-family (signed/unsigned) => DECIMAL(p, s) when the integer digits fit
within (p - s)
- DECIMAL(p, s=0) / INTEGER-family => APPROXIMATE numerics when the target has
at least as many significant digits
All other cases, including DECIMAL with non-zero scale, remain conservative and
are treated as lossy, to honor the method contract (OK to be incomplete but no
false positives).
The newly supported cases must (at least) be covered appropriately in
_RexLosslessCastTest_.
The method has been introduced in Calcite 1.22 and it's still marked as
experimental despite being [in
use|https://github.com/search?q=repo%3Aapache/calcite%20isLosslessCast&type=code]
for years now in several key components, this ticket also proposes promote it
to "stable".
was:
[RexUtil.java#isLossLessCast|https://github.com/apache/calcite/blob/calcite-1.40.0/core/src/main/java/org/apache/calcite/rex/RexUtil.java#L1692]
doesn't handle casts from the INT family to non-INT numeric are not covered at
all and always considered lossy.
This ticket proposes to detect the following additional cases as being lossless:
- INTEGER-family (excluding BIGINT) → DOUBLE
- SMALLINT/TINYINT → REAL
- INTEGER-family → DECIMAL(p,s) is lossless iff the integer part capacity (p -
s) is large enough (10 for INTEGER, 19 for BIGINT, etc.)
The newly supported cases must (at least) be covered appropriately in
_RexLosslessCastTest_.
The method has been introduced in Calcite 1.22 and it's still marked as
experimental despite being [in
use|https://github.com/search?q=repo%3Aapache/calcite%20isLosslessCast&type=code]
for years now in several key components, this ticket also proposes promote it
to "stable".
> Improve detection of lossless casts from INT family to FLOAT/REAL/DECIMAL
> -------------------------------------------------------------------------
>
> Key: CALCITE-7174
> URL: https://issues.apache.org/jira/browse/CALCITE-7174
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Affects Versions: 1.40.0
> Reporter: Alessandro Solimando
> Assignee: Alessandro Solimando
> Priority: Minor
>
> [RexUtil.java#isLossLessCast|https://github.com/apache/calcite/blob/calcite-1.40.0/core/src/main/java/org/apache/calcite/rex/RexUtil.java#L1692]
> doesn't handle casts from the INT family to non-INT numeric are not covered
> at all and always considered lossy.
> This ticket proposes to detect the following additional cases as being
> lossless:
> - INTEGER-family (signed and unsigned) => INTEGER-family when the target
> range fully covers the source range, checked via numeric limits
> - DECIMAL(p, s=0) => INTEGER-family when the decimal range is entirely
> contained in the target integer range
> - INTEGER-family (signed/unsigned) => DECIMAL(p, s) when the integer digits
> fit within (p - s)
> - DECIMAL(p, s=0) / INTEGER-family => APPROXIMATE numerics when the target
> has at least as many significant digits
> All other cases, including DECIMAL with non-zero scale, remain conservative
> and are treated as lossy, to honor the method contract (OK to be incomplete
> but no false positives).
> The newly supported cases must (at least) be covered appropriately in
> _RexLosslessCastTest_.
> The method has been introduced in Calcite 1.22 and it's still marked as
> experimental despite being [in
> use|https://github.com/search?q=repo%3Aapache/calcite%20isLosslessCast&type=code]
> for years now in several key components, this ticket also proposes promote
> it to "stable".
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