PPL Lookup #407
PPL Lookup #407
Conversation
Signed-off-by: Kacper Trochimiak <[email protected]>
Signed-off-by: Kacper Trochimiak <[email protected]>
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@salyh thanks for your contribution |
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@YANG-DB any comments on the proposal so far? |
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@rupal-bq @anasalkouz any comments on the proposal so far? |
| while(!root.getChild().isEmpty()) { | ||
| root = root.getChild().get(0); | ||
| } |
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This loop finds the root command as lookup's source table, but we may have multiple lookup commands, such as source=t1 | lookup t2 | ... | lookup t3
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The source=<table> is used to specify the "source" table name.
It's not required to specify (repeat) the name of the "source" table within the lookup command, so I guess finding the root Relation node is OK. Am I missing something?
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| node.getChild().get(0).accept(this, context); | ||
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| //TODO: not sure how to implement appendonly |
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To implement appendonly, the output Project (parent of Join) should be
Project [other fields in source, CASE WHEN isnull('source.copyField) THEN coalesce('source.copyField, 'lookup.copyField) AS copyField ELSE 'lookup.copyField END AS copyField]
+- Join LeftOuter
In CASE WHEN expression1 ELSE expression2, the expression1 is for appendonly (not performing when the source field already exist), the else is for overwriting existing field.
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Doesn't it mean that we need to know list of fields available in the "source" table, in order to build project consisting of two lists:
a list of fields which we want to overwrite with values from the lookup table and a list of fields which should remain untouched?
I'm not sure whether it is possible to retrieve such list of available fields.
Description
Implement PPL Lookup
Issues Resolved
opensearch-project/sql#2651
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