Dear Andrea,
I have modified the ECQL parser to support this kind of expression
if_then_else(area(THE_GEOM)>10.5, 1).
Unfortunately, as you suspected, this has repercussions "(would allow
building filters/expressions that are not valid anymore, not in CQL, nor
in Filter Encoding)."
So I decided to create a parser to transform my expression into a
pattern allowed by geotools.
CASE WHEN area(THE_GEOM)>10 then 5 else 1 end
will be converted to
if_then_else(greater(area(THE_GEOM), 10),5, 1)
Before doing that I have a question.
Is Geotools able to map the if_then_else function into a CASE WHEN
syntax during SQL generation ?
Best regards
Erwan
Le 21/09/2020 à 12:18, Andrea Aime a écrit :
On Mon, Sep 21, 2020 at 11:08 AM Erwan Bocher
<erwan.boc...@univ-ubs.fr <mailto:erwan.boc...@univ-ubs.fr>> wrote:
I'd like to apply more complex expressions as the Case When above. It
seems there is a function closed to the SQL Case When called
if_then_else.
So I try :
Expression expression =
ECQL.toExpression("if_then_else(area(THE_GEOM)>10,5, 1)");
definitions.add(new Definition("EXP", expression));
SimpleFeatureSource transformed =
TransformFactory.transform((SimpleFeatureSource) fs,
"OUTPUT_TABLE_TEST_F", definitions);
Unfortunately, it returns the following exception
Exception in thread "main"
org.geotools.filter.text.cql2.CQLException:
Encountered ">" at line 1, column 28.
Is there a way to execute nested expression with Geotools ECQL
parser ?
It is, but you're mixing filters and expressions in the wrong way.
Filters use expressions, but
they are not expressions. So something like "area(THE_GEOM)>10" is a
filter, it cannot
be nested inside an expression, only inside another filter.
There are filter functions that try to work around this limitation, so
you could write this instead:
if_then_else(greater(area(THE_GEOM), 10),5, 1)
I'd love to see an improvement in GeoTools allowing to treat a Filter
like an Expression that returns
a boolean but... the change would not be trivial, and rife with
repercussions (would allow building
filters/expressions that are not valid anymore, not in CQL, nor in
Filter Encoding).
Cheers
Andrea
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