rdblue commented on a change in pull request #2055:
URL: https://github.com/apache/iceberg/pull/2055#discussion_r559029224
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File path: site/docs/spec.md
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@@ -831,6 +852,29 @@ Each partition field in the fields list is stored as an
object. See the table fo
In some cases partition specs are stored using only the field list instead of
the object format that includes the spec ID, like the deprecated
`partition-spec` field in table metadata. The object format should be used
unless otherwise noted in this spec.
+### Sort Orders
+
+Sort orders are serialized as a list of JSON object, each of which contains
the following fields:
+
+|Field|JSON representation|Example|
+|--- |--- |--- |
+|**`order-id`**|`JSON int`|`1`|
+|**`fields`**|`JSON list: [`<br /> `<sort field JSON>,`<br
/> `...`<br />`]`|`[ {`<br /> ` "transform":
"identity",`<br /> ` "source-id": 2,`<br /> `
"direction": "asc",`<br /> ` "null-order": "nulls-first"`<br
/> `}, {`<br /> ` "transform": "bucket[4]",`<br
/> ` "source-id": 3,`<br /> ` "direction": "desc",`<br
/> ` "null-order": "nulls-last"`<br />`} ]`|
+
+Each sort field in the fields list is stored as an object with the following
properties:
+
+|Field|JSON representation|Example|
+|--- |--- |--- |
+|**`Sort Field`**|`JSON object: {`<br /> `"transform": <transform
JSON>,`<br /> `"source-id": <source id int>,`<br
/> `"direction": <direction string>,`<br
/> `"null-order": <null-order string>`<br />`}`|`{`<br
/> ` "transform": "bucket[4]",`<br /> ` "source-id":
3,`<br /> ` "direction": "desc",`<br /> ` "null-order":
"nulls-last"`<br />`}`|
+
+The following table describes the possible values for the some of the field
within sort field:
+
+|Field|JSON representation|Possible values|
+|--- |--- |--- |
+|**`direction`**|`JSON string`|`"asc", "desc"`|
+|**`null-order`**|`JSON string`|`"nulls-first", "nulls-last"`|
Review comment:
The `Float.compare` implementation in Java will sort `NaN` larger than
any other value and `-NaN` smaller than any other value. I think we should go
with that.
```java
public static int compare(float f1, float f2) {
if (f1 < f2)
return -1; // Neither val is NaN, thisVal is smaller
if (f1 > f2)
return 1; // Neither val is NaN, thisVal is larger
// Cannot use floatToRawIntBits because of possibility of NaNs.
int thisBits = Float.floatToIntBits(f1);
int anotherBits = Float.floatToIntBits(f2);
return (thisBits == anotherBits ? 0 : // Values are equal
(thisBits < anotherBits ? -1 : // (-0.0, 0.0) or (!NaN, NaN)
1)); // (0.0, -0.0) or (NaN, !NaN)
}
```
I think that produces: -NaN < -Infinity < -value < -0 < 0 < value < Infinity
< NaN
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