Kikyou1997 commented on code in PR #8864:
URL: https://github.com/apache/doris/pull/8864#discussion_r979969582
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fe/fe-core/src/main/java/org/apache/doris/statistics/ColumnStats.java:
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@@ -72,16 +75,94 @@ public class ColumnStats {
private float avgSize = -1; // in bytes
private long maxSize = -1; // in bytes
private long numNulls = -1;
- private LiteralExpr minValue;
- private LiteralExpr maxValue;
-
- public static ColumnStats createDefaultColumnStats() {
- ColumnStats columnStats = new ColumnStats();
- columnStats.setAvgSize(1);
- columnStats.setMaxSize(1);
- columnStats.setNdv(1);
- columnStats.setNumNulls(0);
- return columnStats;
+
+ private LiteralExpr minValue = new NullLiteral();
+ private LiteralExpr maxValue = new NullLiteral();
+
+ /**
+ * Return default column statistic.
+ */
+ public static ColumnStats getDefaultColumnStats() {
+ return new ColumnStats();
+ }
+
+ /**
+ * Merge column statistics(the original statistics should not be modified)
+ *
+ * @param left statistics to be merged
+ * @param right statistics to be merged
+ */
+ public static ColumnStats aggColumnStats(ColumnStats left, ColumnStats
right) {
+ // merge ndv
+ long leftNdv = left.getNdv();
+ long rightNdv = right.getNdv();
+
+ if (leftNdv == -1) {
+ leftNdv = rightNdv;
+ } else {
+ leftNdv = rightNdv != -1 ? (leftNdv + rightNdv) : leftNdv;
+ }
+
+ // merge avg_size
+ float leftAvgSize = left.getAvgSize();
+ float rightAvgSize = right.getAvgSize();
+ if (leftAvgSize == -1) {
+ leftAvgSize = rightAvgSize;
+ } else {
+ leftAvgSize = rightAvgSize != -1 ? ((leftAvgSize + rightAvgSize) /
2) : leftAvgSize;
+ }
+
+ // merge max_size
+ long leftMaxSize = left.getMaxSize();
+ long rightMaxSize = right.getMaxSize();
+ if (leftMaxSize == -1) {
+ leftMaxSize = rightMaxSize;
+ } else {
+ leftMaxSize = rightMaxSize != -1 ? (Math.max(leftMaxSize,
rightMaxSize)) : leftMaxSize;
Review Comment:
`rightMaxSize != -1` here is redundant
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