[IGNITE-23170] SQL returns huge decimal values with trailing zeros

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Fix Version/s: 3.0
• Component/s: sql
• Labels: ignite-3
• Epic Link: AI3 Performance
• Assignee: Unassigned
• Reporter: Pavel Tupitsyn
• Created: 09/Sep/24 10:59
• Updated: 13/Sep/24 08:16

Description

Add the following code to ItSqlApiBaseTest

    @Test
    public void testDecimalDivisionTimeout() {
        IgniteSql igniteSql = igniteSql();

        igniteSql.execute(null, "CREATE TABLE testDecimalDivisionTimeout (ID INT PRIMARY KEY, VAL0 INT)").close();
        for (int i = 0; i < 10; i++) {
            igniteSql.execute(null, "INSERT INTO testDecimalDivisionTimeout VALUES (?, ?)", i, i * 100).close();
        }

        ResultSet<SqlRow> cursor = igniteSql.execute(null,
                "SELECT cast(VAl0 as decimal(300)) / ? FROM testDecimalDivisionTimeout", new BigDecimal(200));

        while (cursor.hasNext()) {
            cursor.next();
        }
    }

Warnings in the log:

org.apache.ignite.lang.IgniteException: A critical thread is blocked for 1758 ms that is more than the allowed 500 ms, it is "iscsat_n_0-client-12" prio=10 Id=121 RUNNABLE
	at java.base@11.0.24/java.math.MutableBigInteger.divideOneWord(MutableBigInteger.java:1131)
	at java.base@11.0.24/java.math.MutableBigInteger.divideKnuth(MutableBigInteger.java:1203)
	at java.base@11.0.24/java.math.MutableBigInteger.divideKnuth(MutableBigInteger.java:1163)
	at java.base@11.0.24/java.math.BigInteger.divideAndRemainderKnuth(BigInteger.java:2328)
	at java.base@11.0.24/java.math.BigInteger.divideAndRemainder(BigInteger.java:2316)
	at java.base@11.0.24/java.math.BigDecimal.createAndStripZerosToMatchScale(BigDecimal.java:4878)
	at java.base@11.0.24/java.math.BigDecimal.stripTrailingZeros(BigDecimal.java:3053)
	at app//org.apache.ignite.internal.binarytuple.BinaryTupleCommon.shrinkDecimal(BinaryTupleCommon.java:118)
	at app//org.apache.ignite.internal.binarytuple.BinaryTupleBuilder.appendDecimalNotNull(BinaryTupleBuilder.java:292)
	at app//org.apache.ignite.internal.binarytuple.BinaryTupleBuilder.appendDecimal(BinaryTupleBuilder.java:317)
	at app//org.apache.ignite.client.handler.requests.sql.ClientSqlCommon.packValue(ClientSqlCommon.java:96)
	at app//org.apache.ignite.client.handler.requests.sql.ClientSqlCommon.packCurrentPage(ClientSqlCommon.java:48)
	at app//org.apache.ignite.client.handler.requests.sql.ClientSqlExecuteRequest.writeResultSetAsync(ClientSqlExecuteRequest.java:135)
	at app//org.apache.ignite.client.handler.requests.sql.ClientSqlExecuteRequest.lambda$process$0(ClientSqlExecuteRequest.java:93)

This is caused by the fact that SQL returns a BigDecimal with ~32000 trailing zeros:

• SqlRowHandler.toBinaryTuple returns "0.5" without trailing zeros - all good
• Commons.readValue sets the scale to 32767, creating trailing zeros, resulting value takes ~3KB
• ClientSqlCommon.packValue calls BinaryTupleBuilder.appendDecimal which takes quite some time to strip those trailing zeros

While IGNITE-18922 will get rid of intermediate conversion in client handler, we still return huge values from embedded API, allocating extra memory and potentially causing issue for the users.

Issue Links

• causes: IGNITE-23204 .NET: TestCastToDecimalPrecision causes other tests to fail
• is related to: IGNITE-18922 Thin 3.0: Avoid BinaryTuple conversion in client SQL handler