Steve Lawrence created DAFFODIL-1877:
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Summary: Slow schema compilation due to unambiguous checks
Key: DAFFODIL-1877
URL: https://issues.apache.org/jira/browse/DAFFODIL-1877
Project: Daffodil
Issue Type: Bug
Components: Front End, Performance
Reporter: Steve Lawrence
Fix For: 2.1.0
Commit 02c8324294ed4395c1231c6ea3ec6ae77139ba46 caused ATO schema compilation
time to jump from about 10 seconds to over 2 minutes. Large increases were also
seen in VMF schema compilation.
Some debugging showed that the cause is likely in the
DFDLPathExpressionCompiler. Wrapping the following code the compiles an
individual expression in a Timer shows an average of 9000% increase in time to
compile.
```scala
val compiler = new DFDLPathExpressionParser[T](qn,
nodeInfoKind, namespaces, compileInfoWherePropertyWasLocated, isEvaluatedAbove)
val compiledDPath = compiler.compile(expr)
compiledDPath
```
So this most likely has something to do with schema compilation. Nothing jumps
out at me in the specified commit as being especially egregious to cause such a
performance degredation. All the really changed was passing an extra parameter
for error accumulation and changing how isReferencedByExpressions is set. I
wouldn't expect that to cause such performance changes. Perhaps it is
findNamedMatches now allocating a Seq?
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