SAP Knowledge Base Article - Preview

3030013 - Optimizer choosing costly merge join when batch SQL with one go - SAP ASE

Symptom

When the same SQLs are batched with multiple commands in single "go", the optimizer chooses the costly merge join over the N-ARY join.

For example,

create table #aa(a1 int)

insert #aa values(1)

select * from aa, bb where aa.a1=bb.b1
go

/* This one is slow

create table #aa(a1 int)
go
insert #aa values(1)
go
select aa.a1 from aa, bb where aa.a1=bb.b1
go

/* This one is quick using N-ARY join


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Environment

SAP Adaptive Server Enterprise (ASE) 15.7

Product

SAP Adaptive Server Enterprise 15.7

Keywords

sp_showplan, sybase, optimizer, nary, N-ARY, nested loop join, 824267, performance
, KBA , BC-SYB-ASE , Sybase ASE Database Platform (non Business Suite) , Bug Filed

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