Github user arina-ielchiieva commented on a diff in the pull request:
https://github.com/apache/drill/pull/685#discussion_r98186438
--- Diff:
exec/java-exec/src/main/java/org/apache/drill/exec/expr/fn/impl/ContextFunctions.java
---
@@ -64,17 +65,45 @@ public void eval() {
@Inject DrillBuf buffer;
@Workspace int currentSchemaBytesLength;
+ @Override
public void setup() {
final byte[] currentSchemaBytes =
contextInfo.getCurrentDefaultSchema().getBytes();
buffer = buffer.reallocIfNeeded(currentSchemaBytes.length);
currentSchemaBytesLength= currentSchemaBytes.length;
buffer.setBytes(0, currentSchemaBytes);
}
+ @Override
public void eval() {
out.start = 0;
out.end = currentSchemaBytesLength;
out.buffer = buffer;
}
}
+
+ /**
+ * Implement "session_id" function. Returns the unique id of the current
session.
+ */
+ @FunctionTemplate(name = "session_id", scope =
FunctionTemplate.FunctionScope.SIMPLE, isNiladic = true)
--- End diff --
Each drill function is converted to DrillFunctionHolder and though Calcite
recognizes current_time/current_date & other context functions (ex: user,
current_schema) as niladic, after introduction of isNilladic flag,
DrillFunctionHolder would describe such functions as non-niladic, though they
are. So we are intentionally hold incorrect info.
Let's say in future I would need to take list of all function holders in
Drill (form local function registry) and filter out all niladic functions,
since we do have such isNiladic flag I would assume that I can use this flag as
filter but since current_time/current_date & other context functions (ex: user,
current_schema) have isniladic=false, they would never be filtered out.
Also please add `isNiladic=true` to other niladic context functions [1].
[1]
https://github.com/apache/drill/blob/5a4ad2a88331dfe7561ee76fc87e882afe170681/exec/java-exec/src/main/java/org/apache/drill/exec/expr/fn/impl/ContextFunctions.java
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