Bug#15581: COALESCE function truncates mutli-byte TINYTEXT values
field.cc: BLOB variations have number-in-bytes limit, unlike CHAR/VARCHAR which have number-of-characters limits. A tinyblob column can store up to 255 bytes. In the case of basic Latin letters (which use 1 byte per character) we can store up to 255 characters in a tinyblob column. When passing an utf8 tinyblob column as an argument into a function (e.g. COALESCE) we need to reserve 3*255 bytes. I.e. multiply length in bytes to mbcharlen for the character set. Although in reality a tinyblob column can never be 3*255 bytes long, we need to set max_length to multiply to make fix_length_and_dec() of the function-caller (e.g. COALESCE) calculate the correct max_length for the column being created. ctype_utf8.result, ctype_utf8.test: Adding test case. mysql-test/t/ctype_utf8.test: Adding test case. mysql-test/r/ctype_utf8.result: Adding test case. sql/field.cc: Bug#15581: COALESCE function truncates mutli-byte TINYTEXT values BLOB variations have byte limits, unlike CHAR/VARCHAR which have number-of-character limits. It means tinyblob can store up to 255 bytes. All of them can be basic latin letters which use 1 byte per character. I.e. we can store up to 255 characters in a tinyblob column. When passing a tinyblob column as an argument into a function (for example COALESCE or CONCAT) we need to reserve 3*255 bytes in the case of utf-8. I.e. multiply length in bytes to mbcharlen for the character set.
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