Airblader commented on a change in pull request #17186:
URL: https://github.com/apache/flink/pull/17186#discussion_r704102162
##########
File path:
flink-table/flink-table-api-java/src/main/java/org/apache/flink/table/api/Expressions.java
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@@ -562,6 +563,43 @@ public static ApiExpression withoutColumns(Object head,
Object... tail) {
return
apiCallAtLeastOneArgument(BuiltInFunctionDefinitions.WITHOUT_COLUMNS, head,
tail);
}
+ /**
+ * Builds a JSON string from a list of key-value pairs.
+ *
+ * <p>{@param keyValues} is an even-numbered list of alternating key/value
pairs. Note that keys
+ * must be non-{@code NULL} string literals, while values may be arbitrary
expressions.
+ *
+ * <p>The {@link JsonOnNull onNull} behavior defines how to treat {@code
NULL} values.
+ *
+ * <p>Note that this function only returns a JSON string, not an actual
JSON type. Not all JSON
+ * can currently be represented in Flink's type system.
+ *
+ * <p>Examples:
+ *
+ * <pre>{@code
+ * // "{}"
+ * jsonObject(JsonOnNull.NULL)
+ * // "{\"K1\":\"V1\",\"K2\":\"V2\"}"
+ * jsonObject(JsonOnNull.NULL, "K1", "V1", "K2", "V2")
+ *
+ * // Expressions as values
+ * jsonObject(JsonOnNull.NULL, "orderNo", $("orderId"))
+ *
+ * // ON NULL
+ * jsonObject(JsonOnNull.NULL, "K1", nullOf(DataTypes.STRING())) //
"{\"K1\":null}"
+ * jsonObject(JsonOnNull.ABSENT, "K1", nullOf(DataTypes.STRING())) // "{}"
+ *
+ * // "{\"K1\":\"{\\\"K2\\\":\\\"V\\\"}\"}"
+ * jsonObject(JsonOnNull.NULL, "K1", jsonObject(JsonOnNull.NULL, "K2",
"V"))
+ * }</pre>
+ */
+ public static ApiExpression jsonObject(JsonOnNull onNull, Object...
keyValues) {
Review comment:
Yes, that would be possible; but we'd basically be rolling our own map
implementation / map utils. I don't think this function is big enough to
warrant having APIs for that as well (and they're kind of un-Flink-y APIs).
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