liquibase-core/src/main/java/liquibase/change/ColumnConfig.java
public ColumnConfig setDefaultValueNumeric(String defaultValueNumeric) {
        if ((defaultValueNumeric == null) || "null".equalsIgnoreCase(defaultValueNumeric)) {
            this.defaultValueNumeric = null;
        } else {
            if ("GENERATED_BY_DEFAULT".equals(defaultValueNumeric)) {
                setAutoIncrement(true);
            } else {
                if (defaultValueNumeric.startsWith("(")) {
                    defaultValueNumeric = defaultValueNumeric.replaceFirst("^\\(", "");
                    defaultValueNumeric = defaultValueNumeric.replaceFirst("\\)$", "");
                }
                try {
                    this.defaultValueNumeric = ValueNumeric.of(Locale.US, defaultValueNumeric);
                } catch (ParseException e) {
                    this.defaultValueComputed = new DatabaseFunction(defaultValueNumeric);
                }
            }
        }

        return this;
    }
public ColumnConfig setDefaultValueNumeric(String defaultValueNumeric) {
        if ((defaultValueNumeric == null) || "null".equalsIgnoreCase(defaultValueNumeric)) {
            this.defaultValueNumeric = null;
        } else {
            if ("GENERATED_BY_DEFAULT".equals(defaultValueNumeric)) {
                setAutoIncrement(true);
            } else {
                if (defaultValueNumeric.startsWith("(")) {
                    defaultValueNumeric = defaultValueNumeric.replaceFirst("^\\(", "");
                    defaultValueNumeric = defaultValueNumeric.replaceFirst("\\)$", "");
                }
                try {
                    this.defaultValueNumeric = ValueNumeric.of(Locale.US, defaultValueNumeric);
                } catch (ParseException e) {
                    this.defaultValueComputed = new DatabaseFunction(defaultValueNumeric);
                }
            }
        }

        return this;
    }
Set the number this column should use as its default. Supports integers and decimals, and strips off any wrapping parentheses.
If the passed value cannot be parsed as a number, it is assumed to be a function that returns a number.
If the value "null" is passed, it will set a null value.
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A special case is made for "GENERATED_BY_DEFAULT" which simply sets the ColumnConfig object to autoIncrement.