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CS122B: Projects in Databases and Web Applications Winter 201 9

CS122B: Projects in Databases and Web Applications Winter 201 9. Professor Chen Li Department of Computer Science UC Irvine Notes 12: User-Defined Functions (UDF) in MySQL. Purpose. SQL has its own limitations Enhance DB using functions implemented in C. Example: edit distance.

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CS122B: Projects in Databases and Web Applications Winter 201 9

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  1. CS122B: Projects in Databases and Web Applications Winter 2019 Professor Chen Li Department of Computer Science UC Irvine Notes 12: User-Defined Functions (UDF) in MySQL

  2. Purpose • SQL has its own limitations • Enhance DB using functions implemented in C

  3. Example: edit distance • Edit distance between two strings is the minimum number of single-character operations (insert/delete/substitute) to transform one to the other • Also known as Levenshtein distance • Example: ed(”schwazeneger”, ”schwarzenegger”) = 2

  4. Dynamicprogrammingfor edit distance

  5. Example • ed(”elephant”, ”relevant”) = 3

  6. Supporting Edit Distance as UDF Compile Edit distance Function in C: ed.c Shared library libed.so CREATE FUNCTION ed RETURNS INTEGER SONAME 'libed.so'; SELECT ed('abc', 'ad'); MySQL

  7. Example: using ed as a UDF • select * from stars where name = ’Arnold schwarzenegger' limit 5 • select * from stars where ed(name, 'Arnold Schwarzeneger') <= 2 limit 5

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