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Optimize Timestamp Formatting #15039

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merged 1 commit into from
Nov 16, 2022
Merged

Optimize Timestamp Formatting #15039

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40 changes: 28 additions & 12 deletions core/trino-spi/src/main/java/io/trino/spi/type/Timestamps.java
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Original file line number Diff line number Diff line change
Expand Up @@ -21,12 +21,12 @@
import static io.trino.spi.type.TimestampType.MAX_PRECISION;
import static java.lang.Math.floorDiv;
import static java.lang.Math.floorMod;
import static java.lang.String.format;
import static java.time.ZoneOffset.UTC;

public class Timestamps
{
private static final DateTimeFormatter TIMESTAMP_FORMATTER = DateTimeFormatter.ofPattern("uuuu-MM-dd HH:mm:ss");
private static final String TIMESTAMP_FORMAT_PATTERN = "uuuu-MM-dd HH:mm:ss";
private static final DateTimeFormatter TIMESTAMP_FORMATTER = DateTimeFormatter.ofPattern(TIMESTAMP_FORMAT_PATTERN);

static final long[] POWERS_OF_TEN = {
1L,
Expand Down Expand Up @@ -141,7 +141,14 @@ static String formatTimestamp(int precision, long epochMicros, int picosOfMicro)
long picoFraction = ((long) floorMod(epochMicros, MICROSECONDS_PER_SECOND)) * PICOSECONDS_PER_MICROSECOND + picosOfMicro;
LocalDateTime dateTime = LocalDateTime.ofInstant(instant, UTC);

return formatTimestamp(precision, dateTime, picoFraction).toString();
StringBuilder builder = new StringBuilder(timestampFormatLength(precision));
formatTimestamp(precision, dateTime, picoFraction, builder);
return builder.toString();
}

private static int timestampFormatLength(int precision)
{
return TIMESTAMP_FORMAT_PATTERN.length() + (precision == 0 ? 0 : precision + 1);
}

static String formatTimestampWithTimeZone(int precision, long epochMillis, int picosOfMilli, ZoneId zoneId)
Expand All @@ -150,20 +157,29 @@ static String formatTimestampWithTimeZone(int precision, long epochMillis, int p
long picoFraction = (long) floorMod(epochMillis, MILLISECONDS_PER_SECOND) * PICOSECONDS_PER_MILLISECOND + picosOfMilli;
LocalDateTime dateTime = LocalDateTime.ofInstant(instant, zoneId);

return formatTimestamp(precision, dateTime, picoFraction)
.append(" ")
.append(zoneId.getId()).toString();
String zoneIdString = zoneId.getId();
StringBuilder builder = new StringBuilder(timestampFormatLength(precision) + zoneIdString.length() + 1);
formatTimestamp(precision, dateTime, picoFraction, builder);
return builder.append(' ').append(zoneIdString).toString();
}

private static StringBuilder formatTimestamp(int precision, LocalDateTime dateTime, long picoFraction)
private static void formatTimestamp(int precision, LocalDateTime dateTime, long picoFraction, StringBuilder builder)
{
StringBuilder builder = new StringBuilder();
builder.append(TIMESTAMP_FORMATTER.format(dateTime));
TIMESTAMP_FORMATTER.formatTo(dateTime, builder);
if (precision > 0) {
long scaledFraction = picoFraction / POWERS_OF_TEN[MAX_PRECISION - precision];
builder.append(".");
builder.append(format("%0" + precision + "d", scaledFraction));
builder.append('.');
builder.setLength(builder.length() + precision);
int index = builder.length() - 1;

// Append the fractional the decimal digits in reverse order
// comparable to format("%0" + precision + "d", scaledFraction);
for (int i = 0; i < precision; i++) {
long temp = scaledFraction / 10;
int digit = (int) (scaledFraction - (temp * 10));
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Why not scaledFraction % 10 ? Is there a measurable performance difference?

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I didn't specifically measure it, this is a variation on the logic inside of Long.toString so I presume it was implemented that way on purpose.

(Long.toString resolves two decimal digits per iteration and therefore also uses lookup tables to convert to char instead of (char)('0' + digit), but that was definitely overkill for this scenario).

scaledFraction = temp;
builder.setCharAt(index - i, (char) ('0' + digit));
}
}
return builder;
}
}