Bug #2628: Streamed grouping fails: "The current-group() function is evaluated repeatedly" - Saxon - Saxonica Developer Community

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Bug #2628

closed

Streamed grouping fails: "The current-group() function is evaluated repeatedly"

Added by Michael Kay almost 9 years ago. Updated almost 8 years ago.

Status:

Closed

Priority:

Normal

Assignee:

Michael Kay

Category:

Streaming

Sprint/Milestone:

Start date:

2016-02-18

Due date:

% Done:

Estimated time:

Legacy ID:

Applies to branch:

9.7

Fix Committed on Branch:

Fixed in Maintenance Release:

Platforms:

Description

Reported here: https://saxonica.plan.io/boards/3/topics/6282

Submitted as an XSLT 3.0 test case si-group-031

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Updated by Michael Kay almost 9 years ago

Status changed from New to In Progress

The problem is that this:

                <xsl:copy select="$root">
                    <xsl:copy-of select="current-group()"/>
                </xsl:copy>

is rewritten internally as

           <xsl:for-each select="$root">
                <xsl:copy>
                    <xsl:copy-of select="current-group()"/>
                </xsl:copy>
            </xsl:for-each>

giving the impression that the current-group() instruction is evaluated repeatedly.

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Updated by Michael Kay almost 9 years ago

I think Saxon may actually be conformant with the streamability rules in the spec here.

19.8.9.4 says current-group() is not streamable if: The path in the construct tree that connects C to the sequence constructor forming the body of F is such that no child construct is a higher-order operand of its parent

But the sequence constructor within xsl:copy[@select] is a higher-order operand of the xsl:copy instruction, because:

The context item for evaluation of O is different from the context item for evaluation of C.

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