selectInBatches: Select in Batches
In girke-lab/ChemmineR-git-svn-bridge: Cheminformatics Toolkit for R

Description Usage Arguments Value Author(s) Examples

When doing a select were the condition is a large number of ids it is not always possible to include them in a single SQL statement. This function will break the list of ids into chunks and send the query for each batch. The resutls are appended and returned as one data frame.

1	selectInBatches(conn, allIndices, genQuery, batchSize = 1e+05)

`conn`	Database connection object
`allIndices`	A vector of indices to pass to the genQuery function in batches.
`genQuery`	A function which takes a vector of indices and constructs an SQL SELECT statement returning records for the given indicies.
`batchSize`	How many indicies to put in each batch.

A data frame with the results of the query as if all inidices had been included in a single SELEcT statement.

Kevin Horan

##---- Should be DIRECTLY executable !! ----
##-- ==>  Define data, use random,
##--	or do  help(data=index)  for the standard data sets.

## The function is currently defined as
function (conn, allIndices, genQuery, batchSize = 1e+05) 
{
    batchByIndex(allIndices, function(indexBatch) {
        df = dbGetQuery(conn, genQuery(indexBatch))
        result = rbind(result, df)
    }, batchSize)
    result
  }