vlsi

When builing large strings with lots of concatenations in PL/SQL, custom approach like "use varchar2(32000) buffer to reduce the number of dbms_lob calls" makes sense even for Oracle 12.1.0.2.0.

The response time improvement is 4..300+ times :) depending on the DB version and API you use.

Note that simple v_clob || TO_CHAR (SYSTIMESTAMP) || ', ' ==> v_clob || TO_CLOB(TO_CHAR (SYSTIMESTAMP) || ', ') trick (note the extra to_clob) makes 24 times improvement for 11g. The trick is bad for 12c where results in 1.5x degradation.

The code was published 4 year ago as an answer to "How to Quickly Append VARCHAR2 to CLOB": http://www.talkapex.com/2009/06/how-to-quickly-append-varchar2-to-clob.html?showComment=1343235921606#c9077980873875311325

vlsi

Links

• https://bugs.openjdk.org/browse/JDK-8321271
• Diff: https://github.com/vlsi/jdk/compare/ce108446ca1fe604ecc24bbefb0bf1c6318271c7...write_bytebuffer
• https://github.com/vlsi/jdk/tree/write_bytebuffer
• https://github.com/vlsi/jdk/blob/write_bytebuffer/test/micro/org/openjdk/bench/java/io/ByteArrayInputStreamTransfer.java

Findings

ByteArrayInputStream.transferTo(BufferedOutputStream) no longer allocates temporary arrays, and it improves performance ~2x for 1MiB inputs.

vlsi

-- This sample reproduces a bug of a "sudden" flip of a server-prepared statement in PG 9.2+
-- In this particular case, backend selects very bad index even though bind values are the same and the table is analyzed

TL;DR: if you want to know true execution plan for a query with bind variables, you must use "prepare...";
       then repeat "explain analyze execute" 6 times :)

-- Note: do not confuse "5 executions before pgjdbc starts to use server-prepared statements" with
--       "first 5 executions of a server-prepared statement before plan flip"

-- Here's discussion in pgsql-hackers list:

vlsi

Generics in Java are hard (sad, but true), however, Kotlin makes them way more accessible 🤩.

Suppose you are doing property-based testing. Just like I suggest, I was creating a jqwik test, and I ran into an issue with generic signatures.

Here's a minimal example, and it already has two issues.

Take a second and find both of them 😉

vlsi

# Run complete. Total time: 00:00:05

Benchmark                                                                  Mode    Cnt     Score     Error   Units
HotspotAllocationProfilerTest.allocateObject                               avgt            4,297             ns/op
HotspotAllocationProfilerTest.allocateObject:·allocated                    avgt           16,002              B/op
HotspotAllocationProfilerTest.allocateObject:·allocation.rate              avgt         3202,343            MB/sec
HotspotAllocationProfilerTest.allocateObjectSampleTime                   sample  15583    56,291 ±   3,064   ns/op
HotspotAllocationProfilerTest.allocateObjectSampleTime:·allocated        sample           16,001              B/op
HotspotAllocationProfilerTest.allocateObjectSampleTime:·allocation.rate  sample         1941,053            MB/sec
HotspotAllocationProfilerTest.allocateObjectSingleShot                       ss      5  1287,800 ± 302,336   ns/op

vlsi

import java.util.concurrent.ThreadLocalRandom

/**
 * This is mostly automatic Java to Kotlin conversion followed with cleanups.
 * See https://twitter.com/tagir_valeev/status/1391615535889137665
 */
object ConcurrentHashMapKotlin {
    class TreeNode<K, V> {
        // red-black tree links
        var parent: TreeNode<K, V>? = null

vlsi

// See https://pegjs.org/online
// Sample expressions:
//   FindBy${Name}
//   FindFirstBy${Name}
//   FindBy${Name}And${OperationType}OrderBy${Name}And${OperationType}DescCount

Query "query"
  = s:Start t:Transform* f:Finalizer?
    { return {start: s, transforms: t, finalizer: f} }

vlsi

// Add Class-Path to the existing "jar" task
tasks.jar {
    val classpath = configurations.runtimeClasspath
    // Input declaration is needed for the proper up-to-date checks
    inputs.files(classpath).withNormalizer(ClasspathNormalizer::class.java)
    manifest {
        attributes(
            "Class-Path" to classpath.map { cp -> cp.joinToString(" ") { it.absolutePath } }
        )
    }

vlsi

Apache Maven enables developers to augment repository URL via settings.xml. That might sound powerful, however, it requires to use the same repository IDs across all the projects which might not be always possible.

Let's see how Gradle-based project can be published to a custom repository.

For instance, let's try to publish Apache Calcite to our own Nexus instance. Of course we don't want to commit the URL and password of our secretNexus to GitHub, so we need to augment the build without touching the files.

Gradle has Initialization Scripts that enable users to augment all the builds without touching project-specific files.

vlsi

Keybase proof

I hereby claim:

• I am vlsi on github.
• I am vlsi (https://keybase.io/vlsi) on keybase.
• I have a public key ASC2sRZGT4IKWFFWjBEznXZ8DHXjdgWnotEDW-x6_eLlYAo

To claim this, I am signing this object: