DEV: document Unicode limitations (#1234)

* DEV: document Unicode limitations

* Apply code review comments

Author: dwdougherty

content/develop/interact/search-and-query/basic-constructs/field-and-type-options.md

@@ -232,4 +232,31 @@ You can search for documents with specific text values using the `<term>` or the
 - Search for a term only in the `title` attribute
     ```
     FT.SEARCH books-idx "@title:dogs"
-    ```
+    ```
+
+## Unicode considerations
+
+Redis Query Engine only supports Unicode characters in the [basic multilingual plane](https://en.wikipedia.org/wiki/Plane_(Unicode)#Basic_Multilingual_Plane); U+0000 to U+FFFF. Unicode characters beyond U+FFFF, such as Emojis, are not supported and would not be retrieved by queries including such characters in the following use cases:
+
+* Querying TEXT fields with Prefix/Suffix/Infix
+* Querying TEXT fields with fuzzy
+
+Examples:
+
+```
+redis> FT.CREATE idx SCHEMA tag TAG text TEXT
+OK
+redis> HSET doc:1 tag '😀😁🙂' text '😀😁🙂'
+(integer) 2
+redis> HSET doc:2 tag '😀😁🙂abc' text '😀😁🙂abc'
+(integer) 2
+redis> FT.SEARCH idx '@text:(*😀😁🙂)' NOCONTENT
+1) (integer) 0
+redis> FT.SEARCH idx '@text:(*😀😁🙂*)' NOCONTENT
+1) (integer) 0
+redis> FT.SEARCH idx '@text:(😀😁🙂*)' NOCONTENT
+1) (integer) 0
+
+redis> FT.SEARCH idx '@text:(%😀😁🙃%)' NOCONTENT
+1) (integer) 0
+```

content/develop/interact/search-and-query/query/full-text.md

@@ -117,4 +117,31 @@ If you want to increase the maximum word distance to two, you can use the follow
 
 {{< clients-example query_ft ft5 >}}
 FT.SEARCH idx:bicycle "%%optamised%%"
-{{< /clients-example >}}
+{{< /clients-example >}}
+
+## Unicode considerations
+
+Redis Query Engine only supports Unicode characters in the [basic multilingual plane](https://en.wikipedia.org/wiki/Plane_(Unicode)#Basic_Multilingual_Plane); U+0000 to U+FFFF. Unicode characters beyond U+FFFF, such as Emojis, are not supported and would not be retrieved by queries including such characters in the following use cases:
+
+* Querying TEXT fields with Prefix/Suffix/Infix
+* Querying TEXT fields with fuzzy
+
+Examples:
+
+```
+redis> FT.CREATE idx SCHEMA tag TAG text TEXT
+OK
+redis> HSET doc:1 tag '😀😁🙂' text '😀😁🙂'
+(integer) 2
+redis> HSET doc:2 tag '😀😁🙂abc' text '😀😁🙂abc'
+(integer) 2
+redis> FT.SEARCH idx '@text:(*😀😁🙂)' NOCONTENT
+1) (integer) 0
+redis> FT.SEARCH idx '@text:(*😀😁🙂*)' NOCONTENT
+1) (integer) 0
+redis> FT.SEARCH idx '@text:(😀😁🙂*)' NOCONTENT
+1) (integer) 0
+
+redis> FT.SEARCH idx '@text:(%😀😁🙃%)' NOCONTENT
+1) (integer) 0
+```