database - How does a DBMS implement their own sorting algorithm? Or do they? -


when sql translated c parser such yacc or bison, piece of translated c code contains the sorting algorithm mathematics? not understand how sorting implemented in dbms (such mysql or microsoft sql server) - algorithm part of grammar parser? or, algorithm applies resulted group of data after fetched sql query, not directly apply computer memory? or sorting algorithm iso standard , dbms required use same algorithm?

i did researched , googling find no clear answer. without unneedingly reading book on database internal, explain concept clearly?

the sorting algorithm not part of grammar parser, it's technically 'implementation detail'. it's rather important 1 though, can fundamentally impact performance of complex queries. term 'implementation detail' refers it's dbms vendor decide , how it.

it partially delegated query optimizer, common sorting algorithms heapsort, mergesort, quicksort et al have different 'best case scenarios'. perform notably better on 'mostly sorted data', , others extremely slow on 'extremely unsorted data'. indexes contain hints on smart dbms pick different sorting algorithm based on data @ hand, see wikipedia writeup comparison. knowledge none of current vendors though.

so in end, sorting algorithms used when black box programmer's perspective. (should) care output sorted correctly.


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