Mark Peng created SOLR-7061:
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Summary: Cross-Entity Variable Resolving and Arguments for
ScriptTransformer Functions
Key: SOLR-7061
URL: https://issues.apache.org/jira/browse/SOLR-7061
Project: Solr
Issue Type: Improvement
Components: contrib - DataImportHandler
Affects Versions: 4.10.3
Reporter: Mark Peng
Priority: Minor
Script Transformer has been widely used to modify the value of columns of
selected rows from targeting data source (such as SQL Database) based on
specific logics, before writing to Solr as documents. However, current
implementation has the following limitations:
*1. It is not possible to pass constant values or resolved variables (e.g.,
$\{TABLE.COLUMN\} ) as arguments to a script function.*
*2. Cross-entity row data exchange is not possible as well.*
In our use case, we have complex nested entities and rely heavily on the script
functions to transform table rows while doing data import. Sometimes for each
single document, we need to get the selected column values from a parent entity
into current entity for doing value transformation and applying if-else logics.
To achieve this, we need to join with others tables in the SQL of current
entity, which is quite resource-consuming, especially for large tables.
Therefore, we have done some improvements to allow us to pass selected column
values from entity A to another entity B as its function arguments by utilizing
variable resolver.
Here is an example about how it works. Support we have the following
configuration:
{code}
<dataConfig>
<dataSource name="ProductDB"
driver="oracle.jdbc.driver.OracleDriver"
url="jdbc:oracle:thin:@${dataimporter.request.host}:${dataimporter.request.port}/${dataimporter.request.name}"
user="${dataimporter.request.user}"
password="${dataimporter.request.password}"
autoCommit="true"/>
<!-- ScriptTransformer functions -->
<script><![CDATA[
function processItemRow(row, resolvedVars) {
var isOnSale = resolvedVars.get("${PRODUCT.IS_ONSALE}");
var discount = row.get("DISCOUNT_RATE");
var price = row.get("PRICE");
if(isOnSale) {
row.put("PRICE", price * discount);
}
else
row.put("PRICE", price);
return row;
}
]]>
</script>
<document name="EC_SHOP">
<entity dataSource="ProductDB" name="PRODUCT"
query="SELECT PRODUCT_ID, TITLE, IS_ONSALE FROM PRODUCT">
<field column="PRODUCT_ID" name="PRODUCT_ID"/>
<field column="TITLE" name="TITLE"/>
<field column="IS_ONSALE" name="IS_ONSALE"/>
<entity dataSource="ProductDB" name="ITEM"
transformer="script:processItemRow(${PRODUCT.IS_ONSALE})"
query="SELECT PRICE FROM ITEM WHERE PRODUCT_ID =
'${PRODUCT.PRODUCT_ID}'">
<field column="PRICE" name="PRICE"/>
</entity>
</entity>
</dataConfig>
{code}
As demonstrated above, now we can get access to the value of column *IS_ONSALE*
of table *PRODUCT* from the entity of table *ITEM* by passing
*$\{PRODUCT.IS_ONSALE\}* as an argument of the function *processItemRow* to
determine if we should give some discounts for the production price. The
signature of function has a secondary argument (named *resolvedVars* here) for
passing the map of column values resolved from other previous entities.
This improvement gives more flexibility for script functions to exchange row
data cross entities and do more complex processing for entity rows.
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