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feat: support scientific notation in parse_float_as_decimal #8494

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feat: support scientific notation in parse_float_as_decimal #8494

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b325670
support scientific notation
Weijun-H Dec 11, 2023
b64e41b
parse number to i16
Weijun-H Dec 11, 2023
48fd865
use BigDecimal
Weijun-H Dec 15, 2023
c6d6e28
fix ci
Weijun-H Dec 15, 2023
5098b17
fix ci
Weijun-H Dec 15, 2023
b04084a
fix ci
Weijun-H Dec 15, 2023
b50d5c1
fix ci
Weijun-H Dec 15, 2023
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14 changes: 14 additions & 0 deletions datafusion-cli/Cargo.lock
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1 change: 1 addition & 0 deletions datafusion/sql/Cargo.toml
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Original file line number Diff line number Diff line change
Expand Up @@ -39,6 +39,7 @@ unicode_expressions = []
[dependencies]
arrow = { workspace = true }
arrow-schema = { workspace = true }
bigdecimal = { workspace = true }
datafusion-common = { workspace = true }
datafusion-expr = { workspace = true }
log = { workspace = true }
Expand Down
63 changes: 40 additions & 23 deletions datafusion/sql/src/expr/value.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -17,8 +17,9 @@

use crate::planner::{ContextProvider, PlannerContext, SqlToRel};
use arrow::compute::kernels::cast_utils::parse_interval_month_day_nano;
use arrow::datatypes::DECIMAL128_MAX_PRECISION;
use arrow_schema::DataType;
use arrow::datatypes::{ArrowNativeTypeOp, DECIMAL128_MAX_PRECISION};
use arrow_schema::{DataType, DECIMAL128_MAX_SCALE};
use bigdecimal::BigDecimal;
use datafusion_common::{
not_impl_err, plan_err, DFSchema, DataFusionError, Result, ScalarValue,
};
Expand All @@ -30,6 +31,7 @@ use log::debug;
use sqlparser::ast::{BinaryOperator, Expr as SQLExpr, Interval, Value};
use sqlparser::parser::ParserError::ParserError;
use std::borrow::Cow;
use std::str::FromStr;

impl<'a, S: ContextProvider> SqlToRel<'a, S> {
pub(crate) fn parse_value(
Expand Down Expand Up @@ -405,39 +407,48 @@ const fn try_decode_hex_char(c: u8) -> Option<u8> {
}

/// Parse Decimal128 from a string
///
/// TODO: support parsing from scientific notation
fn parse_decimal_128(unsigned_number: &str, negative: bool) -> Result<Expr> {
// remove leading zeroes
let trimmed = unsigned_number.trim_start_matches('0');
// parse precision and scale, remove decimal point if exists
let (precision, scale, replaced_str) = if trimmed == "." {
// special cases for numbers such as “0.”, “000.”, and so on.
(1, 0, Cow::Borrowed("0"))
} else if let Some(i) = trimmed.find('.') {
let big_decimal = BigDecimal::from_str(unsigned_number).map_err(|e| {
DataFusionError::from(ParserError(format!(
"Cannot parse {unsigned_number} into BigDecimal when building decimal: {e}"
)))
})?;

let replaced_str = big_decimal.to_string().replace('.', "");
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Once you have parsed the data into a BigDecimal, I think you could just convert to a i128 directly which would be more performant and I think potentially more correct

Perhaps you could use
https://docs.rs/bigdecimal/latest/bigdecimal/struct.BigDecimal.html#method.fractional_digit_count to get the scale

And then compute the precision and the i128 from
https://docs.rs/bigdecimal/latest/bigdecimal/struct.BigDecimal.html#method.into_bigint_and_exponent


let (precision, scale) = if big_decimal.fractional_digit_count() < 0 {
(
trimmed.len() - 1,
trimmed.len() - i - 1,
Cow::Owned(trimmed.replace('.', "")),
(replaced_str.len() as i64)
.add_checked(big_decimal.fractional_digit_count())? as u64,
big_decimal.fractional_digit_count(),
)
} else {
// no decimal point, keep as is
(trimmed.len(), 0, Cow::Borrowed(trimmed))
(
replaced_str.len() as u64,
big_decimal.fractional_digit_count(),
)
};

// check precision overflow
if precision > DECIMAL128_MAX_PRECISION as u64 {
return Err(DataFusionError::from(ParserError(format!(
"Cannot parse {unsigned_number} as i128 when building decimal: precision overflow"
))));
}

// check scale overflow
if scale < -DECIMAL128_MAX_SCALE as i64 || scale > DECIMAL128_MAX_SCALE as i64 {
return Err(DataFusionError::from(ParserError(format!(
"Cannot parse {unsigned_number} as i128 when building decimal: scale overflow"
))));
}

let number = replaced_str.parse::<i128>().map_err(|e| {
DataFusionError::from(ParserError(format!(
"Cannot parse {replaced_str} as i128 when building decimal: {e}"
)))
})?;

// check precision overflow
if precision as u8 > DECIMAL128_MAX_PRECISION {
return Err(DataFusionError::from(ParserError(format!(
"Cannot parse {replaced_str} as i128 when building decimal: precision overflow"
))));
}

Ok(Expr::Literal(ScalarValue::Decimal128(
Some(if negative { -number } else { number }),
precision as u8,
Expand Down Expand Up @@ -468,4 +479,10 @@ mod tests {
assert_eq!(output, expect);
}
}

#[test]
fn test_parse_128_decimal_number() {
let number = "1.23456e10";
parse_decimal_128(number, false).unwrap();
}
}
4 changes: 2 additions & 2 deletions datafusion/sql/tests/sql_integration.rs
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Expand Up @@ -43,8 +43,8 @@ fn parse_decimals() {
let test_data = [
("1", "Int64(1)"),
("001", "Int64(1)"),
("0.1", "Decimal128(Some(1),1,1)"),
("0.01", "Decimal128(Some(1),2,2)"),
("0.1", "Decimal128(Some(1),2,1)"),
("0.01", "Decimal128(Some(1),3,2)"),
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("1.0", "Decimal128(Some(10),2,1)"),
("10.01", "Decimal128(Some(1001),4,2)"),
(
Expand Down
22 changes: 17 additions & 5 deletions datafusion/sqllogictest/test_files/options.slt
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Original file line number Diff line number Diff line change
Expand Up @@ -147,7 +147,7 @@ select .0 as c1, 0. as c2, 0000. as c3, 00000.00 as c4
query TTTT
select arrow_typeof(.0) as c1, arrow_typeof(0.) as c2, arrow_typeof(0000.) as c3, arrow_typeof(00000.00) as c4
----
Decimal128(1, 1) Decimal128(1, 0) Decimal128(1, 0) Decimal128(2, 2)
Decimal128(2, 1) Decimal128(1, 0) Decimal128(1, 0) Decimal128(3, 2)
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query RR
select 999999999999999999999999999999999999, -999999999999999999999999999999999999
Expand Down Expand Up @@ -193,19 +193,31 @@ select arrow_typeof(00009999999999999999999999999999999999.9999),
Decimal128(38, 4) Decimal128(38, 4) Decimal128(20, 0)

# precision overflow
statement error DataFusion error: SQL error: ParserError\("Cannot parse 123456789012345678901234567890123456789 as i128 when building decimal: precision overflow"\)
statement error DataFusion error: SQL error: ParserError\("Cannot parse 123456789.012345678901234567890123456789 as i128 when building decimal: precision overflow"\)
select 123456789.012345678901234567890123456789

statement error SQL error: ParserError\("Cannot parse 123456789012345678901234567890123456789 as i128 when building decimal: precision overflow"\)
statement error SQL error: ParserError\("Cannot parse 123456789.012345678901234567890123456789 as i128 when building decimal: precision overflow"\)
select -123456789.012345678901234567890123456789

# can not fit in i128
statement error SQL error: ParserError\("Cannot parse 1234567890123456789012345678901234567890 as i128 when building decimal: number too large to fit in target type"\)
statement error SQL error: ParserError\("Cannot parse 123456789.0123456789012345678901234567890 as i128 when building decimal: precision overflow"\)
select 123456789.0123456789012345678901234567890

statement error SQL error: ParserError\("Cannot parse 1234567890123456789012345678901234567890 as i128 when building decimal: number too large to fit in target type"\)
statement error SQL error: ParserError\("Cannot parse 123456789.0123456789012345678901234567890 as i128 when building decimal: precision overflow"\)
select -123456789.0123456789012345678901234567890

# scientific notation
query RRRR
select 1.234e2, 1.234e-2, -1.234e2, -1.234e-2
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1.234e-2 is not -123.4 I don't think 🤔

DataFusion CLI v33.0.0
❯ select 1.234e-2;
+------------------+
| Float64(0.01234) |
+------------------+
| 0.01234          |
+------------------+

----
123.4 0.01234 -123.4 -0.01234

statement error DataFusion error: SQL error: ParserError\("Cannot parse 1.234e-40 as i128 when building decimal: precision overflow"\)
select 1.234e-40

statement error DataFusion error: SQL error: ParserError\("Cannot parse 12340000000000000000000000000000000000000 as i128 when building decimal: number too large to fit in target type"\)
select 1.234e+40

# Restore option to default value
statement ok
set datafusion.sql_parser.parse_float_as_decimal = false;