Hi Jan,

Can you explain a little bit more about this? Or is there a Wiki page that explains it? I'm rather curious about what you mean by "duplicate generating path step operator" Maurice.

Jan Rittinger wrote:

Update of /cvsroot/monetdb/pathfinder/compiler/include In directory sc8-pr-cvs7.sourceforge.net:/tmp/cvs-serv28492/include

Modified Files: logical.h logical_mnemonic.h Log Message: -- Introduced a new duplicate generating path step operator. This operator is introduced in the proxy detection phase and replaces the following pattern by a new dup_scjoin operator:

     |X|
   __/ \__
  /       \
 (pi)      |
 |         |
scjoin   (pi)

/ | | (pi) | __ __/ \ / #

The new operator keeps all the columns of its right argument -- the left argument refers to the fragment information -- and adds a new column (stored in the semantical field scjoin.item_res) based on the context column (stored in the semantical field scjoin.item). Because the result may change the cardinality all the other columns are mapped based on the input context nodes.

Index: logical_mnemonic.h

RCS file: /cvsroot/monetdb/pathfinder/compiler/include/logical_mnemonic.h,v retrieving revision 1.14 retrieving revision 1.15 diff -u -d -r1.14 -r1.15 --- logical_mnemonic.h 27 Sep 2006 12:03:51 -0000 1.14 +++ logical_mnemonic.h 13 Nov 2006 09:58:40 -0000 1.15 @@ -134,6 +134,7 @@

/** staircase join */ #define scjoin(a,b,c,d,e,f,g) PFla_scjoin ((a),(b),(c),(d),(e),(f),(g)) +#define dup_scjoin(a,b,c,d,e,f) PFla_dup_scjoin ((a),(b),(c),(d),(e),(f))

/** document table */ #define doc_tbl(a,b,c,d) PFla_doc_tbl((a),(b),(c),(d))

Index: logical.h

RCS file: /cvsroot/monetdb/pathfinder/compiler/include/logical.h,v retrieving revision 1.25 retrieving revision 1.26 diff -u -d -r1.25 -r1.26 --- logical.h 31 Oct 2006 09:32:45 -0000 1.25 +++ logical.h 13 Nov 2006 09:58:40 -0000 1.26 @@ -87,8 +87,9 @@ iteration (Pathfinder extension) */ , la_all = 44 /**< test if all items in an iteration are true */ , la_scjoin = 50 /**< staircase join */

• , la_doc_tbl = 51 /**< document relation (is also a fragment) */
• , la_doc_access = 52 /**< document access necessary for pf:string-value */

• , la_dup_scjoin = 51 /**< staircase join */
• , la_doc_tbl = 52 /**< document relation (is also a fragment) */
• , la_doc_access = 53 /**< document access necessary for pf:string-value */ , la_element = 60 /**< element-constructing operator */ , la_element_tag = 61 /**< part of the element-constructing operator; connecting element tag and content;

@@ -604,6 +605,16 @@ PFalg_att_t iter, PFalg_att_t item, PFalg_att_t item_res);

+/**

• • Staircase join without duplicates between two relations.
• • Each such join corresponds to the evaluation of an XPath
• • location step.
• */

+PFla_op_t * PFla_dup_scjoin (const PFla_op_t *doc, const PFla_op_t *n,

•                         PFalg_axis_t axis, PFty_t seqty,
  

•                         PFalg_att_t item,
  

•                         PFalg_att_t item_res);
  

/*********** node construction functionality *************/

/*

---

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