com.netflix.astyanax.cql.reads

Class CFRowRangeQueryGen

java.lang.Object

com.netflix.astyanax.cql.reads.CFRowSliceQueryGen

com.netflix.astyanax.cql.reads.CFRowRangeQueryGen

public class CFRowRangeQueryGen
extends CFRowSliceQueryGen

This class encapsulates all the query generators for row range queries. There are different row query generators depending on the specific query signature. e.g 1. Select all columns for all the rows in the row range 2. Select row ranges with column slice 3. Select row ranges with column range 4. Select row ranges using a composite range builder for composite column based schema Note that for simplicity and brevity, there is another class that handles similar operations for queries that specify a collection of row keys as opposed to a row range. See CFRowKeysQueryGen for that implementation. The current class is meant for row range queries only. Each of the query generators uses the QueryGenCache so that it can cache the PreparedStatement as well for future use by queries with the same signatures. But one must use this with care, since the subsequent query must have the exact signature, else binding values with the previously constructed prepared statement will break. Here is a simple example of a bad query that is not cacheable. Say that we want a simple query with a column range in it. ks.prepareQuery(myCF) .getRow("1") .withColumnSlice("colStart") .execute(); In most cases this query lends itself to a CQL3 representation as follows SELECT * FROM ks.mfCF WHERE KEY = ? AND COLUMN1 > ?; Now say that we want to perform a successive query (with caching turned ON), but add to the column range query ks.prepareQuery(myCF) .getRow("1") .withColumnSlice("colStart", "colEnd") .execute(); NOTE THE USE OF BOTH colStart AND colEnd <----- THIS IS A DIFFERENT QUERY SIGNATURE AND THE CQL QUERY WILL PROBABLY LOOK LIKE SELECT * FROM ks.mfCF WHERE KEY = ? AND COLUMN1 > ? AND COLUMN1 < ?; <----- NOTE THE EXTRA BIND MARKER AT THE END FOR THE colEnd If we re-use the previously cached prepared statement, then it will not work for the new query signature. The way out of this is to NOT use caching with different query signatures.

Field Summary

Fields inherited from class com.netflix.astyanax.cql.reads.CFRowSliceQueryGen

allPrimayKeyCols, BIND_MARKER, cfDef, clusteringKeyCols, isCompositeColumn, keyspace, partitionKeyCol, regularCols, sessionRef

Constructor Summary

Constructors

Constructor and Description
CFRowRangeQueryGen(com.datastax.driver.core.Session session, java.lang.String keyspaceName, CqlColumnFamilyDefinitionImpl cfDefinition) Constructor

Method Summary

Modifier and Type	Method and Description
com.datastax.driver.core.BoundStatement	getQueryStatement(CqlRowSliceQueryImpl<?,?> rowSliceQuery, boolean useCaching) Main method used to generate the query for the specified row slice query.

Methods inherited from class com.netflix.astyanax.cql.reads.CFRowSliceQueryGen

addWhereClauseForColumnRange, addWhereClauseForCompositeColumnRange, bindMarkerArray, bindWhereClauseForColumnRange, bindWhereClauseForCompositeColumnRange, selectAllColumnsFromKeyspaceAndCF

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

CFRowRangeQueryGen

public CFRowRangeQueryGen(com.datastax.driver.core.Session session,
                          java.lang.String keyspaceName,
                          CqlColumnFamilyDefinitionImpl cfDefinition)

Constructor

Parameters:

session -

keyspaceName -

cfDefinition -

Method Detail

getQueryStatement

public com.datastax.driver.core.BoundStatement getQueryStatement(CqlRowSliceQueryImpl<?,?> rowSliceQuery,
                                                                 boolean useCaching)

Main method used to generate the query for the specified row slice query. Note that depending on the query signature, the caller may choose to enable/disable caching

Parameters:

rowSliceQuery: - The Astaynax query for which we need to generate a java driver query

useCaching: - boolean condition indicating whether we should use a previously cached prepared stmt or not. If false, then the cache is ignored and we generate the prepared stmt for this query If true, then the cached prepared stmt is used. If the cache has not been inited, then the prepared stmt is constructed for this query and subsequently cached

Returns:

BoundStatement: they statement for this Astyanax query