com.ibm.jaql.lang.expr.io.HadoopTempExpr.java Source code

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Here is the source code for com.ibm.jaql.lang.expr.io.HadoopTempExpr.java

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/*
 * Copyright (C) IBM Corp. 2008.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */
package com.ibm.jaql.lang.expr.io;

import java.util.Map;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;

import com.ibm.jaql.io.Adapter;
import com.ibm.jaql.json.schema.RecordSchema;
import com.ibm.jaql.json.schema.Schema;
import com.ibm.jaql.json.schema.SchemaFactory;
import com.ibm.jaql.json.schema.StringSchema;
import com.ibm.jaql.json.type.BufferedJsonRecord;
import com.ibm.jaql.json.type.JsonRecord;
import com.ibm.jaql.json.type.JsonSchema;
import com.ibm.jaql.json.type.JsonString;
import com.ibm.jaql.lang.core.Context;
import com.ibm.jaql.lang.expr.core.ConstExpr;
import com.ibm.jaql.lang.expr.core.Expr;
import com.ibm.jaql.lang.expr.core.ExprProperty;
import com.ibm.jaql.lang.expr.function.DefaultBuiltInFunctionDescriptor;
import com.ibm.jaql.lang.expr.function.JsonValueParameter;
import com.ibm.jaql.lang.expr.function.JsonValueParameters;
import com.ibm.jaql.util.DeleteFileTask;

/** Creates a file descriptor for temporary files used by Jaql. Takes a schema argument that
 * describes the schema of the individual values written to the file. */
public class HadoopTempExpr extends Expr {
    public static final class Descriptor extends DefaultBuiltInFunctionDescriptor {
        public Descriptor() {
            super("HadoopTemp", HadoopTempExpr.class, new JsonValueParameters(new JsonValueParameter("schema",
                    SchemaFactory.schematypeSchema(), new JsonSchema(SchemaFactory.anySchema()))),
                    SchemaFactory.recordSchema());
        }
    }

    /**
     * @param exprs
     */
    public HadoopTempExpr(Expr... exprs) {
        super(exprs);
    }

    public HadoopTempExpr(JsonSchema schema) {
        this(new ConstExpr(schema));
    }

    public HadoopTempExpr(Schema schema) {
        this(new JsonSchema(schema));
    }

    public Map<ExprProperty, Boolean> getProperties() {
        Map<ExprProperty, Boolean> result = super.getProperties();
        result.put(ExprProperty.HAS_SIDE_EFFECTS, true);
        return result;
    }

    /**
     * 
     */
    public HadoopTempExpr() {
        super(NO_EXPRS);
    }

    @Override
    public Schema getSchema() {
        // determine options 
        RecordSchema.Field options[] = new RecordSchema.Field[1];
        options[0] = new RecordSchema.Field(new JsonString("schema"), SchemaFactory.schematypeSchema(), false);
        if (exprs[0].isCompileTimeComputable().always()) {
            try {
                JsonSchema schema = (JsonSchema) exprs[0].compileTimeEval();
                options[0] = new RecordSchema.Field(new JsonString("schema"), SchemaFactory.schemaOf(schema),
                        false);
            } catch (Exception e) {
                // ignore
            }
        }

        // compute result
        RecordSchema.Field fields[] = new RecordSchema.Field[3];
        fields[0] = new RecordSchema.Field(Adapter.LOCATION_NAME, SchemaFactory.stringSchema(), false);
        fields[1] = new RecordSchema.Field(Adapter.TYPE_NAME, new StringSchema(new JsonString("jaqltemp")), false);
        fields[2] = new RecordSchema.Field(Adapter.OPTIONS_NAME,
                new RecordSchema(options, SchemaFactory.anySchema()), false);

        // return resutl
        return new RecordSchema(fields, null);
    }

    /*
     * (non-Javadoc)
     * 
     * @see com.ibm.jaql.lang.Expr#eval(com.ibm.jaql.lang.Context)
     */
    public JsonRecord eval(Context context) throws Exception {
        String filename = "jaqltemp_" + System.nanoTime(); // FIXME: figure out where this should go
        BufferedJsonRecord r = new BufferedJsonRecord();
        r.add(Adapter.TYPE_NAME, new JsonString("jaqltemp"));
        r.add(Adapter.LOCATION_NAME, new JsonString(filename));
        BufferedJsonRecord options = new BufferedJsonRecord();
        JsonSchema schema = (JsonSchema) exprs[0].eval(context);
        options.add(new JsonString("schema"), schema);
        r.add(Adapter.OPTIONS_NAME, options);

        Configuration conf = new Configuration(); // TODO: where to get this from?
        Path path = new Path(filename);
        FileSystem fs = path.getFileSystem(conf);
        context.doAtReset(new DeleteFileTask(fs, path));
        return r; // TODO: memory
    }
}