R/sjdbcGetResultSet.R

In sjdbc: JDBC Driver Interface

"sjdbcGetResultSet"<-
function(key, unregister = TRUE, default.num.rows = NULL,
         start.at.first=TRUE, rows.to.read=-1)
{
    # [Adapted from javaGetResultSet() in S-PLUS 8.0.4]
    #
    # Get the data from the ResultSet into the statics in 
    # SJDBCResultSetUtilities.  Returns NULL if key not recognized.
    #
    # key: String giving the key into the Hashtable in SJDBCResultSetUtilities.  The
    #      ResultSet needs to be put into this Hashtable in Java.
    # unregister: Should the ResultSet be removed from the Hashtable after the 
    #             data is retrieved.
    # default.num.rows: When the ResultSet is of type ResultSet.TYPE_FORWARD_ONLY, 
    #             the number of rows cannot be determined until after all of
    #             the data has been retrieved.  If the ResultSet has more than
    #             the default number, the array sizes will be doubled whenever the
    #             current capacity is reached.  If the ResultSet is not of
    #             TYPE_FORWARD_ONLY, this is not used.
    # start.at.first : if true, set the ResultSet to start with the first row before
    #             reading.  Otherwise, start with the current row.
    # rows.to.read : if less than zero, read all rows in the result set.  Otherwise,
    #             this is the maximum number of rows to read.
    className <- "SJDBCResultSetUtilities"
    if(!is.null(default.num.rows)) {
        .JavaMethod(className, "setDefaultNumberOfRows", "(I)V", 
            default.num.rows)
    }
    
    .JavaMethod(className, "snextPopulateData", 
        "(Ljava/lang/String;ZI)V", key, start.at.first, rows.to.read)
        
    colNames <- .JavaMethod(className, "snextGetColNames", "(Ljava/lang/String;)[Ljava/lang/String;", key) 
    colTypeCodes <- .JavaMethod(className, "snextGetColTypeCodes", "(Ljava/lang/String;)[I", key) 
    data <- data.frame()
    for (i in 1:length(colTypeCodes)) {
        if (colTypeCodes[i] %in% c(2,8)) 
            colData <- .JavaMethod(className, "snextGetDoubleColumn", "(Ljava/lang/String;I)[D", key, i-1)
        #else if (colTypeCodes[i] == 6) 
        #   colData <- .JavaMethod(className, "snextGetFloatColumn", "(Ljava/lang/String;I)[F", key, i-1)
        else if (colTypeCodes[i] == 4)
            colData <- .JavaMethod(className, "snextGetIntegerColumn", "(Ljava/lang/String;I)[I", key, i-1)
        else if (colTypeCodes[i] == -7) 
            colData <- .JavaMethod(className, "snextGetBooleanColumn", "(Ljava/lang/String;I)[Z", key, i-1)
        else  colData <- .JavaMethod(className, "snextGetStringColumn", "(Ljava/lang/String;I)[Ljava/lang/String;", key, i-1)
        
        if (ncol(data) == 0) data <- data.frame(colData) else data <- data.frame(data, colData)
    }
    
    names(data) <- colNames
    
    # Release the data
    .JavaMethod(className, "snextReleaseData", "(Ljava/lang/String;)V", key)
    
    # Release the ResultSet reference
    if(unregister) {
        .JavaMethod(className, "unregister", "(Ljava/lang/String;)V",
            key)
    }
    
    # Can use the colTypes to convert Date, Time, Timestamp, and
    # possibly other classes to similar S-PLUS classes.  
    # Uses strings to pass data back in standard JDBC format
    # due to loss-of-precision when passing back as doubles and
    # reconverting to julian/millisecond values.  
    ## 91 - Date, 92 - Time, 93 - Timestamp
    pos <- match(colTypeCodes, c(91, 92, 93))
    pos <- (1:length(pos))[!is.na(pos)]
    if(length(pos) > 0) {
        for(i in 1:length(pos)) {
            data[, pos[i]] <- as.POSIXct(as.character(data[, pos[i]]), 
                format="%Y-%m-%d %H:%M:%S")
        }
    }
    return(data)
}