Make alias optional

Signed-off-by: Hendrik Saly <hendrik.saly@eliatra.com>
opensearch-project · Oct 30, 2024 · 2c04f75 · 2c04f75
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diff --git a/docs/ppl-lang/ppl-trendline-command.md b/docs/ppl-lang/ppl-trendline-command.md
@@ -5,13 +5,13 @@ Using ``trendline`` command to calculate moving averages of fields.
 
 
 ### Syntax
-`TRENDLINE [sort <[+|-] sort-field>] SMA(number-of-datapoints, field) AS alias`
+`TRENDLINE [sort <[+|-] sort-field>] SMA(number-of-datapoints, field) [AS alias]`
 
 * [+|-]: optional. The plus [+] stands for ascending order and NULL/MISSING first and a minus [-] stands for descending order and NULL/MISSING last. **Default:** ascending order and NULL/MISSING first.
 * sort-field: mandatory when sorting is used. The field used to sort.
-* number-of-datapoints: mandatory. number of datapoints to calculate the moving average.
+* number-of-datapoints: mandatory. number of datapoints to calculate the moving average (must be a positive integer).
 * field: mandatory. the name of the field the moving average should be calculated for.
-* alias: mandatory. the name of the resulting column containing the moving average.
+* alias: optional. the name of the resulting column containing the moving average.
 
 And the moment only the Simple Moving Average (SMA) type is supported.
 

diff --git a/ppl-spark-integration/src/main/antlr4/OpenSearchPPLParser.g4 b/ppl-spark-integration/src/main/antlr4/OpenSearchPPLParser.g4
@@ -254,7 +254,7 @@ trendlineCommand
    ;
 
 trendlineClause
-   : trendlineType LT_PRTHS numberOfDataPoints = integerLiteral COMMA field = fieldExpression RT_PRTHS AS alias = qualifiedName
+   : trendlineType LT_PRTHS numberOfDataPoints = integerLiteral COMMA field = fieldExpression RT_PRTHS (AS alias = qualifiedName)?
    ;
 
 trendlineType

diff --git a/ppl-spark-integration/src/main/java/org/opensearch/sql/ppl/parser/AstBuilder.java b/ppl-spark-integration/src/main/java/org/opensearch/sql/ppl/parser/AstBuilder.java
@@ -405,7 +405,7 @@ private Trendline.TrendlineComputation toTrendlineComputation(OpenSearchPPLParse
       throw new SyntaxCheckException("Number of trendline data-points must be greater than or equal to 0");
     }
     Field dataField = (Field) expressionBuilder.visitFieldExpression(ctx.field);
-    String alias = ctx.alias.getText();
+    String alias = ctx.alias == null?dataField.getField().toString()+"_trendline":ctx.alias.getText();
     String computationType = ctx.trendlineType().getText();
     return new Trendline.TrendlineComputation(numberOfDataPoints, dataField, alias, computationType);
   }