VasShabu commented on code in PR #28850:
URL: https://github.com/apache/flink/pull/28850#discussion_r3705569265
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flink-table/flink-table-runtime/src/main/java/org/apache/flink/table/runtime/functions/SqlJsonUtils.java:
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@@ -446,6 +459,107 @@ private static Object dejsonize(String input) {
return JSON_PATH_JSON_PROVIDER.parse(input);
}
+ /**
+ * Returns an upper-case flag describing the type of the parsed JSON
value, mirroring Calcite's
+ * {@code JsonFunctions.jsonType}.
+ *
+ * <p>JSON's grammar cannot express a date, and it has a single number
rule with no width, so
+ * {@code DATE} and {@code FLOAT} cannot be read off the Java type the
parser produces: a date
+ * arrives as a {@link String}, and every non-integral number arrives as a
{@link BigDecimal}
+ * (the shared mapper enables {@code USE_BIG_DECIMAL_FOR_FLOATS}). Both
flags are therefore
+ * inferred from the value itself, which is a deliberate Flink extension
beyond Calcite:
+ *
+ * <ul>
+ * <li>{@code DATE} for a string that is exactly a {@code yyyy-MM-dd}
calendar date, e.g.
+ * {@code "2015-01-01"}, which is the form the JSON format uses to
read a {@code DATE}
+ * column. Nothing else counts. This is stricter than {@code CAST(x
AS DATE)}, which also
+ * coerces {@code 2015-1-1}, {@code 2015-01} and {@code 2015}; those
are
+ * recognition-unsafe here, since {@code "2015"} is a perfectly
ordinary string.
+ * Date-times stay {@code STRING} in every spelling: there is no
timestamp flag to return,
+ * and answering {@code DATE} for a value carrying a time of day
would be worse than
+ * saying nothing. Flink has no single date-time spelling to defer
to either — {@code
+ * CAST}/{@code TO_TIMESTAMP} accept only a space separator, the
JSON format accepts a
Review Comment:
this para has been cuz because i have dropped the date type
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