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" 
<https://tvtropes.org/pmwiki/pmwiki.php/Main/LudicrousSpeed> 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.

On Tuesday, January 9, 2024 at 8:26:58 AM UTC-5 mche...@gmail.com wrote:

> no, my program use 20 mins keep inserting to H2 (embed + in memory), both 
> speed become stable and nearly the same.
>
> On Tuesday 9 January 2024 at 01:30:44 UTC+8 Andreas Reichel wrote:
>
>> Because its cached and data are written to disk only eventually when the 
>> cache is full?
>>
>> On Mon, 2024-01-08 at 09:20 -0800, mche...@gmail.com wrote:
>>
>> 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 <310-7200>;PAGE_SIZE=10240;CACHE_TYPE=SOFT_LRU;", "sa", "");
>> // Connection conn = 
>> DriverManager.getConnection("jdbc:h2:mem:test;CACHE_SIZE=13107200 
>> <310-7200>;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();
>> }
>> }
>>
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