GENERATE_SERIES function #8795

sim1984 · 2025-10-30T17:13:40Z

GENERATE_SERIES function

The GENERATE_SERIES function creates a series of numbers within a specified interval.
The interval and the step between series values are defined by the user.

Syntax

<generate_series_function> ::=
    GENERATE_SERIES(<start>, <finish> [, <step>]) [AS] <correlation name> [ ( <derived column name> ) ]

Arguments

start - The first value in the interval. start is specified as a variable, a literal, or a scalar expression of type
smallint, integer, bigint or numeric(18, x).
finish - The last value in the interval. finish is specified as a variable, a literal, or a scalar expression of
type smallint, integer, bigint or numeric(18, x). The series stops once the last generated step value exceeds
the finish value.
step - Indicates the number of values to increment or decrement between steps in the series. step is an expression
of type smallint, integer, bigint or numeric(18, x). step can be either negative or positive, but can't be zero (0). This
argument is optional. The default value for step is 1.

Returning type

The function GENERATE_SERIES returns a set with BIGINT or NUMERIC(18, x) column, where the scale is
determined by the maximum of the scales of the function arguments.

Rules

If start > finish and a negative step value is specified, an empty set is returned.
If start < finish and a positive step value is specified, an empty set is returned.
If the step argument is zero, an error is thrown.

Examples

SELECT n
FROM GENERATE_SERIES(1, 3) AS S(n);

SELECT n
FROM GENERATE_SERIES(3, 1, -1) AS S(n);

SELECT n
FROM GENERATE_SERIES(0, 9.9, 0.1) AS S(n);

SELECT 
  DATEADD(n MINUTE TO timestamp '2025-01-01 12:00') AS START_TIME,
  DATEADD(n MINUTE TO timestamp '2025-01-01 12:00:59.9999') AS FINISH_TIME
FROM GENERATE_SERIES(0, 59) AS S(n);

A similar function exists in PostgreSQL: https://www.postgresql.org/docs/current/functions-srf.html and in MS SQL 2022: https://learn.microsoft.com/en-us/sql/t-sql/functions/generate-series-transact-sql?view=sql-server-ver17

PostgreSQL has the ability to generate date and time sequences, but we don't have interval types, so this isn't implemented. However, by generating a sequence of numbers, we can generate any sequence.

sim1984 · 2025-10-30T17:17:02Z

PSQL procedure vs built-in function performance test

CREATE EXCEPTION E_INVALID_STEP 'Procedure SP_GENERATE_SERIES required values of parameter STEP_VALUE non equal zero';

SET TERM ^;

CREATE OR ALTER PROCEDURE SP_GENERATE_SERIES (
  START_VALUE  BIGINT,
  FINISH_VALUE BIGINT,
  STEP_VALUE   BIGINT DEFAULT 1)
RETURNS (
  CURRENT_VALUE BIGINT)
AS
BEGIN
  IF (STEP_VALUE = 0) THEN EXCEPTION E_INVALID_STEP;
  IF (STEP_VALUE > 0) THEN
    FOR CURRENT_VALUE = START_VALUE TO FINISH_VALUE BY STEP_VALUE DO
      SUSPEND;
  IF (STEP_VALUE < 0) THEN
    FOR CURRENT_VALUE = START_VALUE DOWNTO FINISH_VALUE BY ABS(STEP_VALUE) DO
      SUSPEND;
END^

SET TERM ;^

1000000 records

SELECT 
  COUNT(*), MIN(CURRENT_VALUE), MAX(CURRENT_VALUE)
FROM SP_GENERATE_SERIES(1, 1000000);


                COUNT                   MIN                   MAX
===================== ===================== =====================
              1000000                     1               1000000

Current memory = 19793200
Delta memory = 240
Max memory = 19869584
Elapsed time = 0.294 sec
Buffers = 2048
Reads = 0
Writes = 0
Fetches = 0

SELECT 
  COUNT(*), MIN(N), MAX(N)
FROM GENERATE_SERIES(1, 1000000) S(N);


                COUNT                   MIN                   MAX
===================== ===================== =====================
              1000000                     1               1000000

Current memory = 19809936
Delta memory = 208
Max memory = 19869616
Elapsed time = 0.047 sec
Buffers = 2048
Reads = 0
Writes = 0
Fetches = 0

10000000 records

SELECT 
  COUNT(*), MIN(CURRENT_VALUE), MAX(CURRENT_VALUE)
FROM SP_GENERATE_SERIES(1, 10000000);


                COUNT                   MIN                   MAX
===================== ===================== =====================
             10000000                     1              10000000

Current memory = 19828352
Delta memory = 240
Max memory = 36589008
Elapsed time = 2.867 sec
Buffers = 2048
Reads = 0
Writes = 0
Fetches = 0

SELECT 
  COUNT(*), MIN(N), MAX(N)
FROM GENERATE_SERIES(1, 10000000) S(N);

                COUNT                   MIN                   MAX
===================== ===================== =====================
             10000000                     1              10000000

Current memory = 19844848
Delta memory = 208
Max memory = 19869616
Elapsed time = 0.453 sec
Buffers = 2048
Reads = 0
Writes = 0
Fetches = 0

aafemt · 2025-10-30T17:22:19Z

It is a system selectable procedure with fixed number of parameters and output. Why did you create a new BLR verb instead of using existing BLR for calling it by name?

sim1984 · 2025-10-30T17:29:00Z

It is a system selectable procedure with fixed number of parameters and output. Why did you create a new BLR verb instead of using existing BLR for calling it by name?

We don't have any system stored procedures, except for those in system packages.
The output type takes the maximum scale of the arguments.

dyemanov · 2025-10-30T17:35:58Z

It is a system selectable procedure with fixed number of parameters and output. Why did you create a new BLR verb instead of using existing BLR for calling it by name?

This PR correctly extends blr_table_value_fun with a new subcode, it does not introduce a new BLR code. This was added exactly to implement new table-valued functions (and they may have non-procedure-like syntax).

aafemt · 2025-10-30T17:40:38Z

2. The output type takes the maximum scale of the arguments.

It can be handled at DSQL stage.

This PR correctly extends blr_table_value_fun with a new subcode, it does not introduce a new BLR code.

Ugh, I see.

hvlad

Just a few little notes.

src/jrd/recsrc/TableValueFunctionScan.cpp

src/jrd/RecordSourceNodes.cpp

src/jrd/RecordSourceNodes.h

asfernandes · 2025-10-31T00:37:35Z

doc/sql.extensions/README.generate_series.md

+## Arguments
+
+* `start` - The first value in the interval. `start` is specified as a variable, a literal, or a scalar expression of type 
+`smallint`, `integer`, `bigint` or `numeric(18, x)`.


What about INT128?

asfernandes · 2025-10-31T00:41:31Z

src/dsql/parse.y

+		}
+	;
+
+%type <valueExprNode> step_opt


I'd call it comma_value_opt.

asfernandes · 2025-10-31T00:44:49Z

src/jrd/RecordSourceNodes.cpp

+	DsqlDescMaker::fromNode(dsqlScratch, &stepDesc, stepItem, true);
+
+	// common scale
+	const auto scale = MIN(MIN(startDesc.dsc_scale, finishDesc.dsc_scale), stepDesc.dsc_scale);


It's documented to be the max, but here you use min.

asfernandes · 2025-10-31T00:45:56Z

src/jrd/RecordSourceNodes.cpp

+
+	if (!field)
+	{
+		const auto newField = FB_NEW_POOL(dsqlScratch->getPool()) dsql_fld(dsqlScratch->getPool());


I'd use field directly without that extra newField.

asfernandes · 2025-10-31T00:48:14Z

src/jrd/RecordSourceNodes.h

 	}
 };

+class GenSeriesFunctionSourceNode : public TableValueFunctionSourceNode


I'd say it's better to declare the class as final instead of each method. Methods should be declared with override.

asfernandes · 2025-10-31T00:48:51Z

src/jrd/RecordSourceNodes.h

+class GenSeriesFunctionSourceNode : public TableValueFunctionSourceNode
+{
+public:
+	explicit GenSeriesFunctionSourceNode(MemoryPool& pool) : TableValueFunctionSourceNode(pool)


It's not the common convention to put : ... in the same line as the constructor.

asfernandes · 2025-10-31T00:50:16Z

src/jrd/recsrc/RecordSource.h


+	class GenSeriesFunctionScan final : public TableValueFunctionScan
+	{
+		enum GenSeriesTypeItemIndex : unsigned


Why unsigned instead of UCHAR?

Isn't enum class a much more elegant thing than use common prefix for legacy enums?

asfernandes · 2025-10-31T00:51:22Z

src/jrd/recsrc/RecordSource.h

+		GenSeriesFunctionScan(CompilerScratch* csb, StreamType stream, const Firebird::string& alias,
+						   ValueListNode* list);
+
+	protected:


Use override in methods.

asfernandes · 2025-10-31T00:53:10Z

src/jrd/recsrc/TableValueFunctionScan.cpp

+	}
+
+	// common scale
+	const auto scale = MIN(MIN(startDesc->dsc_scale, finishDesc->dsc_scale), stepDesc->dsc_scale);


asfernandes · 2025-10-31T00:58:55Z

src/jrd/recsrc/TableValueFunctionScan.cpp

+
+	rpb->rpb_number.increment();
+
+	do


I didn't go to suggest better thing, but for me this code and m_recordExists is very confusing.

sim1984 added 2 commits October 29, 2025 19:34

GENERATE_SERIES function

46c836b

don't use temp space

e2c86bd

hvlad reviewed Oct 30, 2025

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fixed after hvlad review

8f660b8

asfernandes reviewed Oct 31, 2025

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GENERATE_SERIES function #8795

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GENERATE_SERIES function #8795

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sim1984 commented Oct 30, 2025

GENERATE_SERIES function

Syntax

Arguments

Returning type

Rules

Examples

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sim1984 commented Oct 30, 2025 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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PSQL procedure vs built-in function performance test

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aafemt commented Oct 30, 2025

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sim1984 commented Oct 30, 2025

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dyemanov commented Oct 30, 2025

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sim1984 commented Oct 30, 2025 •

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