MySQL Incorrect string value error - mysql

Question

In a Django application with MySQL DB back-end users try to insert notes which contain some smileys and hearts and stuff which are Unicode characters. MySQL refuses the operations with an error:
(1366, "Incorrect string value: '\\xE2\\x9D\\xA4\\xEF\\xB8\\x8F' for column 'note' at row 1")
(The column in question has longtext type. The Unicode characters in this case valid, it's a heart and a modifier https://codepoints.net/U+2764 https://codepoints.net/U+FE0F, so it's not that they would be 4 byte long UTF-8 characters. I made sure that MySQL's default character set is utf-8.)
What is interesting is that I cannot fully reproduce this error on my local developer environment. One particular difference is that it only emits a warning for that anomaly.
Update1:
This is still bothering to me:
mysql> SELECT default_character_set_name FROM information_schema.SCHEMATA WHERE schema_name="sblive";
+----------------------------+
| default_character_set_name |
+----------------------------+
| latin1 |
+----------------------------+
1 row in set (0.00 sec)
I converted the specific table's charset to utf-8:
mysql> alter table uploads_uploads convert to character set utf8 COLLATE utf8_general_ci;
Query OK, 1209036 rows affected (1 min 10.31 sec)
Records: 1209036 Duplicates: 0 Warnings: 0
mysql> SELECT character_set_name FROM information_schema.`COLUMNS` WHERE table_schema = "sblive" AND table_name = "uploads_uploads" AND column_name = "note";
+--------------------+
| character_set_name |
+--------------------+
| utf8 |
+--------------------+
1 row in set (0.00 sec)
mysql> SHOW VARIABLES LIKE '%char%';
+--------------------------+----------------------------+
| Variable_name | Value |
+--------------------------+----------------------------+
| character_set_client | utf8 |
| character_set_connection | utf8 |
| character_set_database | latin1 |
| character_set_filesystem | binary |
| character_set_results | utf8 |
| character_set_server | utf8 |
| character_set_system | utf8 |
| character_sets_dir | /usr/share/mysql/charsets/ |
+--------------------------+----------------------------+
8 rows in set (0.01 sec)
mysql> SHOW VARIABLES LIKE '%colla%';
+----------------------+-------------------+
| Variable_name | Value |
+----------------------+-------------------+
| collation_connection | utf8_general_ci |
| collation_database | latin1_swedish_ci |
| collation_server | utf8_unicode_ci |
+----------------------+-------------------+
3 rows in set (0.00 sec)

Answer 1

You are asking for ❤️ followed by a "non-spacing" "VARIATION SELECTOR-16".
Your bytes are utf8 -- good
Your connection needs to specify utf8 -- does it?
Your TEXT column need to be declared CHARACTER SET utf8 -- is it? Use SHOW CREATE TABLE to verify.
If you are using HTML, it needs to say charset=UTF-8 -- does it?
Suggest you switch to utf8mb4 if the 'back-end users' are likely to enter more emoticons -- the 'Emoji' will need it.
Addenda
Let's check the data... Please run this
SELECT col, HEX(col) FROM ...
Those two character should deliver hex E29DA4 and EFB88F. If you see C3A2C29DC2A4C3AFC2B8C28F, you have "double encoding", which is a messier problem. 2764FE0F would indicate utf16, I think.