why insert many record to in-memory database is same speed as embedded-mode

[mche...@gmail.com]

hi.
   why insert many record to in-memory database is same speed as embedded-mode. In-mem should be much faster, right?

import java.io.FileNotFoundException;
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.sql.Statement;
import me.tongfei.progressbar.ProgressBar;
import org.junit.Test;

/**
 *
 * @author peter
 */
public class TestH2InsertSpeed {

@Test
public void test() throws FileNotFoundException, IOException, SQLException {

Connection conn = DriverManager.getConnection("jdbc:h2:./test;CACHE_SIZE=13107200;PAGE_SIZE=10240;CACHE_TYPE=SOFT_LRU;", "sa", "");
// Connection conn = DriverManager.getConnection("jdbc:h2:mem:test;CACHE_SIZE=13107200;PAGE_SIZE=10240;CACHE_TYPE=SOFT_LRU;");
Statement stmt2 = conn.createStatement();
stmt2.execute("drop table if exists qemu;");
stmt2.execute("""
  CREATE TABLE "PUBLIC"."QEMU"
  (
     "ID" integer auto_increment PRIMARY KEY NOT NULL,
     "SEQUENCE" bigint,
     "DATE" timestamp,
     "COMPUTER" varchar(50),
     "INTERRUPT" boolean,
     "INTERRUPT_CAUSE" bigint,
     "INTERRUPT_DESC" varchar(30),
     "PC" bigint NOT NULL,
     "MHARTID" bigint NOT NULL,
     "MSTATUS" bigint NOT NULL,
     "HSTATUS" bigint NOT NULL,
     "VSSTATUS" bigint NOT NULL,
     "MIP" bigint NOT NULL,
     "MIE" bigint NOT NULL,
     "MIDELEG" bigint NOT NULL,
     "HIDELEG" bigint NOT NULL,
     "MEDELEG" bigint NOT NULL,
     "HEDELEG" bigint NOT NULL,
     "MTVEC" bigint NOT NULL,
     "STVEC" bigint NOT NULL,
     "VSTVEC" bigint NOT NULL,
     "MEPC" bigint NOT NULL,
     "SEPC" bigint NOT NULL,
     "VSEPC" bigint NOT NULL,
     "MCAUSE" bigint NOT NULL,
     "SCAUSE" bigint NOT NULL,
     "VSCAUSE" bigint NOT NULL,
     "MTVAL" bigint NOT NULL,
     "STVAL" bigint NOT NULL,
     "HTVAL" bigint NOT NULL,
     "MTVAL2" bigint NOT NULL,
     "MSCRATCH" bigint NOT NULL,
     "SSCRATCH" bigint NOT NULL,
     "SATP" bigint NOT NULL,
     "X0_ZERO" bigint NOT NULL,
     "X1_RA" bigint NOT NULL,
     "X2_SP" bigint NOT NULL,
     "X3_GP" bigint NOT NULL,
     "X4_TP" bigint NOT NULL,
     "X5_T0" bigint NOT NULL,
     "X6_T1" bigint NOT NULL,
     "X7_T2" bigint NOT NULL,
     "X8_S0" bigint NOT NULL,
     "X9_S1" bigint NOT NULL,
     "X10_A0" bigint NOT NULL,
     "X11_A1" bigint NOT NULL,
     "X12_A2" bigint NOT NULL,
     "X13_A3" bigint NOT NULL,
     "X14_A4" bigint NOT NULL,
     "X15_A5" bigint NOT NULL,
     "X16_A6" bigint NOT NULL,
     "X17_A7" bigint NOT NULL,
     "X18_S2" bigint NOT NULL,
     "X19_S3" bigint NOT NULL,
     "X20_S4" bigint NOT NULL,
     "X21_S5" bigint NOT NULL,
     "X22_S6" bigint NOT NULL,
     "X23_S7" bigint NOT NULL,
     "X24_S8" bigint NOT NULL,
     "X25_S9" bigint NOT NULL,
     "X26_S10" bigint NOT NULL,
     "X27_S11" bigint NOT NULL,
     "X28_T3" bigint NOT NULL,
     "X29_T4" bigint NOT NULL,
     "X30_T5" bigint NOT NULL,
     "X31_T6" bigint NOT NULL,
     "LINENO" bigint,
     "CODE" varchar(200),
     "MEM" boolean,
     "MEMOPERATION" varchar(200),
     "MEMREAD" boolean,
     "MEMADDR" bigint,
     "MEMVALUE" bigint,
     "MEMSIZE" integer,
     "CCODE" varchar(100),
     "PRIV" integer,
     "IRQREQUEST" boolean,
     "IRQREQUESTNO" integer,
     "IRQREQUESTLEVEL" integer
  );""");

String sql = "INSERT INTO `qemu` VALUES (default, ?, CURRENT_TIMESTAMP(), 'quantr-ubuntu', ?, ?, ?";
sql += ",?".repeat(59);
sql += ",?,?,?,?,?,?,?,?,?,?,?,?,?)";
PreparedStatement stmt = conn.prepareStatement(sql);

ProgressBar pb = new ProgressBar("Insert H2", 1000);
for (int x1 = 0; x1 < 1000; x1++) {
// System.out.println(x1);
for (int x2 = 0; x2 < 10000; x2++) {
int x = 1;
stmt.setLong(x++, 12345678l);
stmt.setBoolean(x++, true);
stmt.setLong(x++, 12345678l);
stmt.setString(x++, "aslkdjads alksdja ldj");
for (int z = 0; z < 59; z++) {
// System.out.println(me.getKey() + "\t= " + me.getValue());
// System.out.println(">" + me.getKey() + "=" + me.getValue());
stmt.setLong(x++, 12345678l);
}
stmt.setLong(x++, 12345678l);
stmt.setString(x++, "askdjasd aljdlasjdlkaj sd");
stmt.setBoolean(x++, true);
stmt.setString(x++, "peter cheung");
stmt.setBoolean(x++, false);
stmt.setLong(x++, 12345678l);
stmt.setLong(x++, 12345678l);
stmt.setInt(x++, 12345678);
stmt.setString(x++, "asdasd as daasd asda sds das d");
stmt.setInt(x++, 12345678);
stmt.setBoolean(x++, true);
stmt.setInt(x++, 12345678);
stmt.setInt(x++, 12345678);
stmt.addBatch();
}
stmt.executeBatch();
pb.step();
}
pb.refresh();
conn.commit();
conn.close();
}
}

[Andreas Reichel]

Because its cached and data are written to disk only eventually when the cache is full?

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[mche...@gmail.com]

no, my program use 20 mins keep inserting to H2 (embed + in memory), both speed become stable and nearly the same.

[Andrei Tokar]

Apparently, you assumption about "In-mem should be much faster" is not correct.

It just makes me wonder, what exactly is the problem at hand? Is that the disk-based database is too fast?
Or there is an expectation of some "ludicrous speed" for in-memory mode?  8-)
And if speed is not ludicrous enough - compare it with other databases out there. I am genuinely interested to see some results posted here.
Bottleneck most likely is memory manipulation, related to transactions management and non-blocking B-tree access (multi-version store).  Disk writes are done by parallel background threads, and it looks like, they are pretty much free (in this use case).
Some significant short-cuts can be taken under assumption of a single-client use (non-transactional, non-concurrent), but that is the topic for a wish list.

[mche...@gmail.com]

thanks all