Query Optimization in the Presence of Foreign Functions
نویسندگان
چکیده
'l'hl~ cl~.~I~Lrat,iv(~tlc,ss of relational query Iilll~U~@?S is vl*ry ;tttr:tctivc, for dcvt?loping applications. However, IIIA~I~ al~l)licatioiir; also i~ctl to invoke externill func(.ions or to access data that is not stored in the cl;~t.;rh;rsc*. It is IIOI. hard to express ref(xreuces 1.0 such IibrcGgn functions in the query language. However, the isslm ol’ wsl.-Iswxl optimization of relational queries in 1.11~ pr~~s~~ncc of such foreign functions has not previously Iwm addressed satisfactorily. In this paper, WV cl~sc*rihe a comprehensive approach to this problem. Our kcly observation is that the optimization must take into acrount semantic information about, foreign funcl.icms. ‘I’hcreforc, we provide a simple declarative rule
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