Concatenating >2 operands to LONGCHAR takes exponentially longer

When concatenating strings to a LONGCHAR variable within a loop, and the concatenation operation adds more than 2 values within the same statement, the loop takes longer and longer to complete each iteration as the value in the LONGCHAR gets larger

Jan 25, 2018
Knowledge

Title

URL Name

concatenating-2-operands-to-longchar-takes-exponentially-longer

Article Number

000121551

Environment

Product: OpenEdge Version: 11.6.4, 11.7.2 OS: All Supported Platforms

Question/Problem Description

Steps to Reproduce

- Run the below code

Clarifying Information

DEFINE VARIABLE cString  AS CHARACTER   NO-UNDO.

DEFINE VARIABLE lcString AS LONGCHAR    NO-UNDO.

DEFINE VARIABLE iCount   AS INTEGER     NO-UNDO.

ASSIGN cString  = FILL("x",2000)
       lcString = "".

DO iCount = 1 TO 10000:
    lcString = lcString + CHR(10) + cString.
END.

Error Message

Defect Number

Defect PSC00361900

Enhancement Number

Cause

When the ABL interpreter encounters a statement which concatenates more than 2 operands together it handles this concatenation in a loop, allocating a temporary buffer to hold the product of each pair of operands, then concatenates them together at the end.

This is done mid-operation, and the buffer(s) being allocated contain the entire product of the concatenation to-date. This allocation for each pair of operands (particularly when done in a loop) is extremely expensive and takes longer for each iteration (as the original string gets larger).

Resolution

Upgrade to OpenEdge 11.7.3 or later.

Workaround

Split the single-line concatenation into multiple lines.

For example:

DEFINE VARIABLE cString  AS CHARACTER   NO-UNDO.

DEFINE VARIABLE lcString AS LONGCHAR    NO-UNDO.
DEFINE VARIABLE lcTemp   AS LONGCHAR    NO-UNDO.

DEFINE VARIABLE iCount   AS INTEGER     NO-UNDO.

ASSIGN cString  = FILL("x",2000)
       lcString = "".

DO iCount = 1 TO 10000:
    lcTemp = lcString + CHR(10).
    lcString = lcTemp + cString.
END.

Notes

If running an OpenEdge version earlier than 11.6.4 or 11.7.2, the performance difference when using the workaround is unlikely to be perceptible due to the existence of defect# PSC00360959 which caused all LONGCHAR concatenation operations to suffer similar significant performance delays.

References to Other Documentation:
Progress Article(s):
Concatenating to LONGCHAR takes exponentially longer

Keyword Phrase

Last Modified Date

11/20/2020 7:11 AM

Concatenating >2 operands to LONGCHAR takes exponentially longer

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