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https://issues.apache.org/jira/browse/SOLR-2202?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12927895#action_12927895
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Greg Fodor edited comment on SOLR-2202 at 11/3/10 12:34 PM:
------------------------------------------------------------
This update to the patch includes a number of performance enhancements and is
the version of the patch we will be likely to push to production.
First, this patch introduces the defaultCurrency parameter, which defaults to
USD. The default currency allows you to omit the currency code in the field
value (ie, "5000" instead of "5000,USD".) However, it plays a more pivotal role
in improving performance.
The previous patches provided a native approach to constructing the trie
bounding range by taking the max and min currency exchange rates for the target
currency. This proved to be minimally useful since the relative value of
currency units vary wildly and hence the bounding range often spanned the full
document set.
The solution I took in this patch is to compute the bounding range by taking
into account the "currency drift." Before getting to that, though, the indexing
process was updated to include a new dynamic field that indexes the value of
the field in the *default currency*, exchanged at the current rate at indexing
time. (Additionally, a stored field is optionally created if the money field is
marked as stored.)
Now, the appreciative and depreciative drifts of a currency C are defined to be
the difference between the current exchange rate and the peak and trough
exchange rates seen for the life of the index from C to the default currency.
By taking the largest drifts (both appreciating and depreciating) across all
currencies, a optimal and correct bounding range to use for a trie query
against the default currency can be computed.
The historical max and min exchange rates relative to the default currency are
now tracked by solr in a properties file. The properties file is named after
the currency config file. For example, if the config file is "currency.xml",
the properties file is "currency.xml.drift.properties". This file is designed
to work correctly with replication, and is updated by Solr whenever the
currency config file is loaded.
For example, if the default currency is USD, and over the life of the index the
EUR exchange rate to USD is seen to be 1.1, 1.4, and 1.3, the max and min
exchange rates are clearly 1.1 and 1.4. If the current exchange rate at query
time is 1.3, the "depreciative drift" for EUR is 1.3 - 1.1 = 0.2, and the
"appreciative drift" is 1.4 - 1.1 = 0.3. If the query being made is for ($100,
$200), the lower bound is adjusted based upon the depreciative drift to $100 -
(0.2 * $100) = $80, and the upper bound is adjusted based upon the appreciative
drift to $200 + (0.3 * $200) = $260.
This is an accurate bounding range for the indexed default currency value,
since those are the max and min possible values that were indexed regardless of
the time the indexing occured. So, the trie query is formed to query against
the new dynamic field that indexes the original value as the default currency,
over the bounds ($80, $260). The trie query is appended to a boolean clause
that further constrains the results by doing the actual conversion to determine
if the current exchange rate will still yield it as matching the user's range
query.
Beyond this, I added some additional intra-query caching and changed the query
construction from the FilteredQuery approach (which seemed to be inefficient in
leveraging the trie query) to the BooleanQuery. You'll note that I rely upon
the second clause in the BooleanQuery being scored first, which eliminates the
expensive exchange rate conversions from happening for documents that fall
outside the trie range.
I ran into a limitation of the current resource loader API, however, in that it
does not allow access to creating or writing new resources, which is needed to
maintain the drift properties file. For now, I only support SolrResourceLoader
which writes to the local filesystem by extracting the config directory.
However, the new ZkResourceLoader is not supported, for example. A non-fatal
warning is emitted to the log when this occurs. The side effect of this is that
currency exchange rate drift will not be tracked, resulting in incorrect range
and point queries if the currency.xml file is updated. It would be nice if it
were possible to ask the ResourceLoader for an OutputStream to a new resource
for this purpose.
Some limitations:
- The default currency cannot be changed after the initial index, otherwise the
index effectively is corrupt since the value for the trie bound is indexed in
the default currency.
- Loss or corruption of the drift file will cause erroneous range and point
queries (documents will be omitted from the results, though no incorrect
documents will appear.)
- As mentioned above, the only ResourceLoader supported are SolrResourceLoaders
that respond to getConfigDir(). Please let me know if there is a safer, more
canonical way to store and load Solr-maintained metadata that lives with the
index.
Also note that this has been tested with replication. The only thing necessary
for replication to work is that the currency.xml and
currency.xml.drift.properties file be included as part of the replication. A
limitation here is that if no documents are updated but the currency exchange
rates change, the file will not be replicated due to Solr's policy of not
replicating files without index changes. It would be useful to allow this
behavior to be overridden. In our case this isn't a problem since our index
churn is high enough that replication events happen regularly.
In the end these changes result in accurate currency range queries that perform
nearly as fast as their non-currency counterparts.
was (Author: gfodor):
This update to the patch includes a number of performance enhancements and
is the version of the patch we will be likely to push to production.
First, this patch introduces the defaultCurrency parameter, which defaults to
USD. The default currency allows you to omit the currency code in the field
value (ie, "5000" instead of "5000,USD".) However, it plays a more pivotal role
in improving performance.
The previous patches provided a native approach to constructing the trie
bounding range by taking the max and min currency exchange rates for the target
currency. This proved to be minimally useful since the relative value of
currency units vary wildly and hence the bounding range often spanned the full
document set.
The solution I took in this patch is to compute the bounding range by taking
into account the "currency drift." Before getting to that, though, the indexing
process was updated to include a new dynamic field that indexes the value of
the field in the *default currency*, exchanged at the current rate at indexing
time. (Additionally, a stored field is optionally created if the money field is
marked as stored.)
Now, the appreciative and depreciative drifts of a currency C are defined to be
the difference between the current exchange rate and the peak and trough
exchange rates seen for the life of the index to from C to the default
currency. By taking the largest drifts (both appreciating and depreciating)
across all currencies, a optimal and correct bounding range to use for a trie
query against the default currency can be computed.
The historical max and min exchange rates relative to the default currency are
now tracked by solr in a properties file. The properties file is named after
the currency config file. For example, if the config file is "currency.xml",
the properties file is "currency.xml.drift.properties". This file is designed
to work correctly with replication, and is updated by Solr whenever the
currency config file is loaded.
For example, if the default currency is USD, and over the life of the index the
EUR exchange rate to USD is seen to be 1.1, 1.4, and 1.3, the max and min
exchange rates are clearly 1.1 and 1.4. If the current exchange rate at query
time is 1.3, the "depreciative drift" for EUR is 1.3 - 1.1 = 0.2, and the
"appreciative drift" is 1.4 - 1.1 = 0.3. If the query being made is for ($100,
$200), the lower bound is adjusted based upon the depreciative drift to $100 -
(0.2 * $100) = $80, and the upper bound is adjusted based upon the appreciative
drift to $200 + (0.3 * $200) = $260.
This is an accurate bounding range for the indexed default currency value,
since those are the max and min possible values that were indexed regardless of
the time the indexing occured. So, the trie query is formed to query against
the new dynamic field that indexes the original value as the default currency,
over the bounds ($80, $260). The trie query is appended to a boolean clause
that further constrains the results by doing the actual conversion to determine
if the current exchange rate will still yield it as matching the user's range
query.
Beyond this, I added some additional intra-query caching and changed the query
construction from the FilteredQuery approach (which seemed to be inefficient in
leveraging the trie query) to the BooleanQuery. You'll note that I rely upon
the second clause in the BooleanQuery being scored first, which eliminates the
expensive exchange rate conversions from happening for documents that fall
outside the trie range.
I ran into a limitation of the current resource loader API, however, in that it
does not allow access to creating or writing new resources, which is needed to
maintain the drift properties file. For now, I only support SolrResourceLoader
which writes to the local filesystem by extracting the config directory.
However, the new ZkResourceLoader is not supported, for example. A non-fatal
warning is emitted to the log when this occurs. The side effect of this is that
currency exchange rate drift will not be tracked, resulting in incorrect range
and point queries if the currency.xml file is updated. It would be nice if it
were possible to ask the ResourceLoader for an OutputStream to a new resource
for this purpose.
Some limitations:
- The default currency cannot be changed after the initial index, otherwise the
index effectively is corrupt since the value for the trie bound is indexed in
the default currency.
- Loss or corruption of the drift file will cause erroneous range and point
queries (documents will be omitted from the results, though no incorrect
documents will appear.)
- As mentioned above, the only ResourceLoader supported are SolrResourceLoaders
that respond to getConfigDir(). Please let me know if there is a safer, more
canonical way to store and load Solr-maintained metadata that lives with the
index.
Also note that this has been tested with replication. The only thing necessary
for replication to work is that the currency.xml and
currency.xml.drift.properties file be included as part of the replication. A
limitation here is that if no documents are updated but the currency exchange
rates change, the file will not be replicated due to Solr's policy of not
replicating files without index changes. It would be useful to allow this
behavior to be overridden. In our case this isn't a problem since our index
churn is high enough that replication events happen regularly.
In the end these changes result in accurate currency range queries that perform
nearly as fast as their non-currency counterparts.
> Money FieldType
> ---------------
>
> Key: SOLR-2202
> URL: https://issues.apache.org/jira/browse/SOLR-2202
> Project: Solr
> Issue Type: New Feature
> Components: Schema and Analysis
> Affects Versions: 1.5
> Reporter: Greg Fodor
> Attachments: SOLR-2022-solr-3.patch, SOLR-2202-lucene-1.patch,
> SOLR-2202-solr-1.patch, SOLR-2202-solr-2.patch, SOLR-2202-solr-4.patch,
> SOLR-2202-solr-5.patch, SOLR-2202-solr-6.patch
>
>
> Attached please find patches to add support for monetary values to
> Solr/Lucene with query-time currency conversion. The following features are
> supported:
> - Point queries (ex: "price:4.00USD")
> - Range quries (ex: "price:[$5.00 TO $10.00]")
> - Sorting.
> - Currency parsing by either currency code or symbol.
> - Symmetric & Asymmetric exchange rates. (Asymmetric exchange rates are
> useful if there are fees associated with exchanging the currency.)
> At indexing time, money fields can be indexed in a native currency. For
> example, if a product on an e-commerce site is listed in Euros, indexing the
> price field as "10.00EUR" will index it appropriately. By altering the
> currency.xml file, the sorting and querying against Solr can take into
> account fluctuations in currency exchange rates without having to re-index
> the documents.
> The new "money" field type is a polyfield which indexes two fields, one which
> contains the amount of the value and another which contains the currency code
> or symbol. The currency metadata (names, symbols, codes, and exchange rates)
> are expected to be in an xml file which is pointed to by the field type
> declaration in the schema.xml.
> The current patch is factored such that Money utility functions and
> configuration metadata lie in Lucene (see MoneyUtil and CurrencyConfig),
> while the MoneyType and MoneyValueSource lie in Solr. This was meant to
> mirror the work being done on the spacial field types.
> This patch has not yet been deployed to production but will be getting used
> to power the international search capabilities of the search engine at Etsy.
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