Andreas Huber
ac1ee20046
LuDB has a few disadvantages.
1. Most notably disk space. H2 wastes a lot of valuable disk space.
For my test data set with 44 million entries it is 14 MB
(sometimes a lot more; depends on H2 internal cleanup). With
data-store it is 15 KB.
Overall I could reduce the disk space from 231 MB to 200 MB (13.4 %
in this example). That is an average of 4.6 bytes per entry.
2. Speed:
a) Liquibase is slow. The first time it takes approx. three seconds
b) Query and insertion. with data-store we can insert entries
up to 1.6 times faster.
Data-store uses a few tricks to save disk space:
1. We encode the tags into the file names.
2. To keep them short we translate the key/value of the tag into
shorter numbers. For example "foo" -> 12 and "bar" to 47. So the
tag "foo"/"bar" would be 12/47.
We then translate this number into a numeral system of base 62
(a-zA-Z0-9), so it can be used for file names and it is shorter.
That way we only have to store the mapping of string to int.
3. We do that in a simple tab separated file.
32 lines
983 B
Java
32 lines
983 B
Java
package org.lucares.pdbui;
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import java.io.IOException;
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import java.nio.file.Path;
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import java.nio.file.Paths;
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import org.lucares.performance.db.PerformanceDb;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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import org.springframework.beans.factory.annotation.Value;
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import org.springframework.context.annotation.Bean;
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import org.springframework.context.annotation.ComponentScan;
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import org.springframework.context.annotation.Configuration;
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import org.springframework.scheduling.annotation.EnableAsync;
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@Configuration
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@EnableAsync
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@ComponentScan("org.lucares.pdbui")
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public class MySpringConfiguration {
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private static final Logger LOGGER = LoggerFactory.getLogger(MySpringConfiguration.class);
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@Bean
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PerformanceDb performanceDb(@Value("${db.base}") final String dbBaseDir) throws IOException {
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final Path dataDirectory = Paths.get(dbBaseDir);
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LOGGER.info("using database in {}", dataDirectory.toAbsolutePath());
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return new PerformanceDb(dataDirectory);
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}
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}
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