1#include <Common/SipHash.h>
2#include <Common/FieldVisitors.h>
3#include <Parsers/ASTLiteral.h>
4#include <IO/WriteHelpers.h>
5
6
7namespace DB
8{
9
10void ASTLiteral::updateTreeHashImpl(SipHash & hash_state) const
11{
12 const char * prefix = "Literal_";
13 hash_state.update(prefix, strlen(prefix));
14 applyVisitor(FieldVisitorHash(hash_state), value);
15}
16
17void ASTLiteral::appendColumnNameImpl(WriteBuffer & ostr) const
18{
19 /// Special case for very large arrays. Instead of listing all elements, will use hash of them.
20 /// (Otherwise column name will be too long, that will lead to significant slowdown of expression analysis.)
21 if (value.getType() == Field::Types::Array
22 && value.get<const Array &>().size() > 100) /// 100 - just arbitrary value.
23 {
24 SipHash hash;
25 applyVisitor(FieldVisitorHash(hash), value);
26 UInt64 low, high;
27 hash.get128(low, high);
28
29 writeCString("__array_", ostr);
30 writeText(low, ostr);
31 ostr.write('_');
32 writeText(high, ostr);
33 }
34 else
35 {
36 String column_name = applyVisitor(FieldVisitorToString(), value);
37 writeString(column_name, ostr);
38 }
39}
40
41}
42