Re: [PATCH] Re: [HACKERS] Adding XMLEXISTS to the grammar
On lör, 2010-07-24 at 20:32 +0100, Mike Fowler wrote: Attached is the revised version of the patch addressing all the issues raised in the review, except for the use of AexprConst and c_expr. With my limited knowledge of bison I've failed to resolve the shift/reduce errors that are introduced by using a_expr. I'm open to suggestions as my desk is getting annoyed with me beating it in frustration! It's committed now. I ended up refactoring this a little bit so that xpath() and xmlexists() can share more of the code. Also, I relaxed the grammar a bit for better compatibility with DB2, Oracle, and Derby. -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [PATCH] Re: [HACKERS] Adding XMLEXISTS to the grammar
On 21/07/10 08:33, Mike Fowler wrote: Why is the first argument AexprConst instead of a_expr? The SQL standard says it's a character string literal, but I think we can very well allow arbitrary expressions. Yes, it was AexprConst because of the specification. I also found that using it solved my shift/reduce problems, but I can change it a_expr as see if I can work them out in a different way. [snip] Why c_expr? As with the AexprConst, it's choice was partially influenced by the fact it solved the shift/reduce errors I was getting. I'm guessing than that I should really use a_expr and resolve the shift/reduce problem differently? Attached is the revised version of the patch addressing all the issues raised in the review, except for the use of AexprConst and c_expr. With my limited knowledge of bison I've failed to resolve the shift/reduce errors that are introduced by using a_expr. I'm open to suggestions as my desk is getting annoyed with me beating it in frustration! Thanks again for taking the time to review my work. Regards, -- Mike Fowler Registered Linux user: 379787 *** a/doc/src/sgml/func.sgml --- b/doc/src/sgml/func.sgml *** *** 8554,8562 SELECT xmlagg(x) FROM (SELECT * FROM test ORDER BY y DESC) AS tab; ]]/screen /para /sect3 !sect3 titleXML Predicates/title indexterm primaryIS DOCUMENT/primary --- 8554,8570 ]]/screen /para /sect3 +/sect2 !sect2 titleXML Predicates/title + + indexterm + primaryXML Predicates/primary + /indexterm + +sect3 + titleIS DOCUMENT/title indexterm primaryIS DOCUMENT/primary *** *** 8574,8579 SELECT xmlagg(x) FROM (SELECT * FROM test ORDER BY y DESC) AS tab; --- 8582,8619 between documents and content fragments. /para /sect3 + +sect3 + titleXMLEXISTS/title + + indexterm + primaryXMLEXISTS/primary + /indexterm + + synopsis + functionXMLEXISTS/function(replaceablexpath/replaceable optionalPASSING BY REF replaceablexml/replaceable optionalBY REF/optional/optional) + /synopsis + + para + The function functionxmlexists/function returns true if the replaceablexpath/replaceable + returns any nodes and false otherwise. If no replaceablexml/replaceable is passed, the function + will return false as a XPath cannot be evaluated without content. See the + ulink url=http://www.w3.org/TR/xpath/#section-Introduction;W3C recommendation 'XML Path Language'/ulink + for a detailed explanation of why. + /para + + para + Example: + screen![CDATA[ + SELECT xmlexists('//town[text() = ''Toronto'']' PASSING BY REF 'townstownToronto/towntownOttawa/town/towns'); + + xmlexists + + t + (1 row) + ]]/screen + /para +/sect3 /sect2 sect2 id=functions-xml-processing *** a/src/backend/parser/gram.y --- b/src/backend/parser/gram.y *** *** 423,431 static TypeName *TableFuncTypeName(List *columns); %type list opt_check_option %type target xml_attribute_el ! %type list xml_attribute_list xml_attributes %type node xml_root_version opt_xml_root_standalone ! %type ival document_or_content %type boolean xml_whitespace_option %type node common_table_expr --- 423,432 %type list opt_check_option %type target xml_attribute_el ! %type list xml_attribute_list xml_attributes xmlexists_list %type node xml_root_version opt_xml_root_standalone ! %type node xmlexists_query_argument_list ! %type ival document_or_content %type boolean xml_whitespace_option %type node common_table_expr *** *** 511,523 static TypeName *TableFuncTypeName(List *columns); OBJECT_P OF OFF OFFSET OIDS ON ONLY OPERATOR OPTION OPTIONS OR ORDER OUT_P OUTER_P OVER OVERLAPS OVERLAY OWNED OWNER ! PARSER PARTIAL PARTITION PASSWORD PLACING PLANS POSITION PRECEDING PRECISION PRESERVE PREPARE PREPARED PRIMARY PRIOR PRIVILEGES PROCEDURAL PROCEDURE QUOTE ! RANGE READ REAL REASSIGN RECHECK RECURSIVE REFERENCES REINDEX RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA RESET RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROW ROWS RULE --- 512,524 OBJECT_P OF OFF OFFSET OIDS ON ONLY OPERATOR OPTION OPTIONS OR ORDER OUT_P OUTER_P OVER OVERLAPS OVERLAY OWNED OWNER ! PARSER PARTIAL PARTITION PASSING PASSWORD PLACING PLANS POSITION PRECEDING PRECISION PRESERVE PREPARE PREPARED PRIMARY PRIOR PRIVILEGES PROCEDURAL PROCEDURE QUOTE ! RANGE READ REAL REASSIGN RECHECK RECURSIVE REF REFERENCES REINDEX RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA RESET RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROW ROWS RULE *** *** 539,545 static TypeName *TableFuncTypeName(List *columns); WHEN WHERE WHITESPACE_P WINDOW WITH WITHOUT WORK WRAPPER WRITE
Re: [PATCH] Re: [HACKERS] Adding XMLEXISTS to the grammar
Hi Peter, Thanks for your feedback. On 20/07/10 19:54, Peter Eisentraut wrote: Attached is a patch with the revised XMLEXISTS function, complete with grammar support and regression tests. The implemented grammar is: XMLEXISTS ( xpath_expression PASSING BY REF xml_value [BY REF] ) Though the full grammar makes everything after the xpath_expression optional, I've left it has mandatory simply to avoid lots of rework of the function (would need new null checks, memory handling would need reworking). Some thoughts, mostly nitpicks: The snippet of documentation could be clearer. It says if the xml satisifies the xpath. Not sure what that means exactly. An XPath expression, by definition, returns a value. How is that value used to determine the result? I'll rephrase it: The function xmlexists returns true if the xpath returns any nodes and false otherwise. Naming of parser symbols: xmlexists_list isn't actually a list of xmlexists's. That particular rule can probably be done away with anyway and the code be put directly into the XMLEXISTS rule. Why is the first argument AexprConst instead of a_expr? The SQL standard says it's a character string literal, but I think we can very well allow arbitrary expressions. Yes, it was AexprConst because of the specification. I also found that using it solved my shift/reduce problems, but I can change it a_expr as see if I can work them out in a different way. xmlexists_query_argument_list should be optional. OK, I'll change it. The rules xml_default_passing_mechanism and xml_passing_mechanism are pretty useless to have a separate rules. Just mention the tokens where they are used. Again, I'll change that too. Why c_expr? As with the AexprConst, it's choice was partially influenced by the fact it solved the shift/reduce errors I was getting. I'm guessing than that I should really use a_expr and resolve the shift/reduce problem differently? Call the C-level function xmlexists for consistency. Sure. I'll look to get a patch addressing these concerns out in the next day or two, work/family/sleep permitting! :) Regards, -- Mike Fowler Registered Linux user: 379787 -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [PATCH] Re: [HACKERS] Adding XMLEXISTS to the grammar
On tis, 2010-06-29 at 12:22 +0100, Mike Fowler wrote: Mike Fowler wrote: Thanks again for your help Robert, turns out the fault was in the pg_proc entry (the 3 up there should've been a two!). Once I took the grammar out it was quickly obvious where I'd gone wrong. Attached is a patch with the revised XMLEXISTS function, complete with grammar support and regression tests. The implemented grammar is: XMLEXISTS ( xpath_expression PASSING BY REF xml_value [BY REF] ) Though the full grammar makes everything after the xpath_expression optional, I've left it has mandatory simply to avoid lots of rework of the function (would need new null checks, memory handling would need reworking). As with the xpath_exists patch I've now added the SGML documentation detailing this function and extended the regression test a little to test XML literals. Some thoughts, mostly nitpicks: The snippet of documentation could be clearer. It says if the xml satisifies the xpath. Not sure what that means exactly. An XPath expression, by definition, returns a value. How is that value used to determine the result? Naming of parser symbols: xmlexists_list isn't actually a list of xmlexists's. That particular rule can probably be done away with anyway and the code be put directly into the XMLEXISTS rule. Why is the first argument AexprConst instead of a_expr? The SQL standard says it's a character string literal, but I think we can very well allow arbitrary expressions. xmlexists_query_argument_list should be optional. The rules xml_default_passing_mechanism and xml_passing_mechanism are pretty useless to have a separate rules. Just mention the tokens where they are used. Why c_expr? Call the C-level function xmlexists for consistency. -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [PATCH] Re: [HACKERS] Adding XMLEXISTS to the grammar
Mike Fowler wrote: Thanks again for your help Robert, turns out the fault was in the pg_proc entry (the 3 up there should've been a two!). Once I took the grammar out it was quickly obvious where I'd gone wrong. Attached is a patch with the revised XMLEXISTS function, complete with grammar support and regression tests. The implemented grammar is: XMLEXISTS ( xpath_expression PASSING BY REF xml_value [BY REF] ) Though the full grammar makes everything after the xpath_expression optional, I've left it has mandatory simply to avoid lots of rework of the function (would need new null checks, memory handling would need reworking). As with the xpath_exists patch I've now added the SGML documentation detailing this function and extended the regression test a little to test XML literals. Regards, -- Mike Fowler Registered Linux user: 379787 *** a/doc/src/sgml/func.sgml --- b/doc/src/sgml/func.sgml *** *** 8554,8562 SELECT xmlagg(x) FROM (SELECT * FROM test ORDER BY y DESC) AS tab; ]]/screen /para /sect3 !sect3 titleXML Predicates/title indexterm primaryIS DOCUMENT/primary --- 8554,8570 ]]/screen /para /sect3 +/sect2 !sect2 titleXML Predicates/title + + indexterm + primaryXML Predicates/primary + /indexterm + +sect3 + titleIS DOCUMENT/title indexterm primaryIS DOCUMENT/primary *** *** 8574,8579 SELECT xmlagg(x) FROM (SELECT * FROM test ORDER BY y DESC) AS tab; --- 8582,8616 between documents and content fragments. /para /sect3 + +sect3 + titleXMLEXISTS/title + + indexterm + primaryXMLEXISTS/primary + /indexterm + + synopsis + functionXMLEXISTS/function(replaceablexpath/replaceable PASSING BY REF replaceablexml/replaceable optionalBY REF/optional) + /synopsis + + para + The function functionxmlexists/function returns true if the replaceablexml/replaceable + satisfies the replaceablexpath/replaceable and false otherwise. + /para + + para + Example: + screen![CDATA[ + SELECT xmlexists('//town[text() = ''Toronto'']' PASSING BY REF 'townstownToronto/towntownOttawa/town/towns'); + + xmlexists + + t + (1 row) + ]]/screen + /para +/sect3 /sect2 sect2 id=functions-xml-processing *** a/src/backend/parser/gram.y --- b/src/backend/parser/gram.y *** *** 423,431 static TypeName *TableFuncTypeName(List *columns); %type list opt_check_option %type target xml_attribute_el ! %type list xml_attribute_list xml_attributes %type node xml_root_version opt_xml_root_standalone ! %type ival document_or_content %type boolean xml_whitespace_option %type node common_table_expr --- 423,432 %type list opt_check_option %type target xml_attribute_el ! %type list xml_attribute_list xml_attributes xmlexists_list %type node xml_root_version opt_xml_root_standalone ! %type node xmlexists_query_argument_list xml_default_passing_mechanism xml_passing_mechanism ! %type ival document_or_content %type boolean xml_whitespace_option %type node common_table_expr *** *** 511,523 static TypeName *TableFuncTypeName(List *columns); OBJECT_P OF OFF OFFSET OIDS ON ONLY OPERATOR OPTION OPTIONS OR ORDER OUT_P OUTER_P OVER OVERLAPS OVERLAY OWNED OWNER ! PARSER PARTIAL PARTITION PASSWORD PLACING PLANS POSITION PRECEDING PRECISION PRESERVE PREPARE PREPARED PRIMARY PRIOR PRIVILEGES PROCEDURAL PROCEDURE QUOTE ! RANGE READ REAL REASSIGN RECHECK RECURSIVE REFERENCES REINDEX RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA RESET RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROW ROWS RULE --- 512,524 OBJECT_P OF OFF OFFSET OIDS ON ONLY OPERATOR OPTION OPTIONS OR ORDER OUT_P OUTER_P OVER OVERLAPS OVERLAY OWNED OWNER ! PARSER PARTIAL PARTITION PASSING PASSWORD PLACING PLANS POSITION PRECEDING PRECISION PRESERVE PREPARE PREPARED PRIMARY PRIOR PRIVILEGES PROCEDURAL PROCEDURE QUOTE ! RANGE READ REAL REASSIGN RECHECK RECURSIVE REF REFERENCES REINDEX RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA RESET RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROW ROWS RULE *** *** 539,545 static TypeName *TableFuncTypeName(List *columns); WHEN WHERE WHITESPACE_P WINDOW WITH WITHOUT WORK WRAPPER WRITE ! XML_P XMLATTRIBUTES XMLCONCAT XMLELEMENT XMLFOREST XMLPARSE XMLPI XMLROOT XMLSERIALIZE YEAR_P YES_P --- 540,546 WHEN WHERE WHITESPACE_P WINDOW WITH WITHOUT WORK WRAPPER WRITE ! XML_P XMLATTRIBUTES XMLCONCAT XMLELEMENT XMLEXISTS XMLFOREST XMLPARSE XMLPI XMLROOT XMLSERIALIZE YEAR_P YES_P *** *** 9806,9811 func_expr: func_name '(' ')' over_clause --- 9807,9828 { $$ = makeXmlExpr(IS_XMLELEMENT, $4, $6, $8,
Re: [PATCH] Re: [HACKERS] Adding XMLEXISTS to the grammar
On Sun, Jun 27, 2010 at 12:04 PM, Mike Fowler m...@mlfowler.com wrote: Thanks again for your help Robert, turns out the fault was in the pg_proc entry (the 3 up there should've been a two!). Once I took the grammar out it was quickly obvious where I'd gone wrong. Glad it was a helpful suggestion. Attached is a patch with the revised XMLEXISTS function, complete with grammar support and regression tests. The implemented grammar is: XMLEXISTS ( xpath_expression PASSING BY REF xml_value [BY REF] ) Though the full grammar makes everything after the xpath_expression optional, I've left it has mandatory simply to avoid lots of rework of the function (would need new null checks, memory handling would need reworking). So if you don't specify the xml_value, what does the xpath_expression get applied to? -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise Postgres Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [PATCH] Re: [HACKERS] Adding XMLEXISTS to the grammar
Robert Haas wrote: On Sun, Jun 27, 2010 at 12:04 PM, Mike Fowler m...@mlfowler.com wrote: Thanks again for your help Robert, turns out the fault was in the pg_proc entry (the 3 up there should've been a two!). Once I took the grammar out it was quickly obvious where I'd gone wrong. Glad it was a helpful suggestion. Attached is a patch with the revised XMLEXISTS function, complete with grammar support and regression tests. The implemented grammar is: XMLEXISTS ( xpath_expression PASSING BY REF xml_value [BY REF] ) Though the full grammar makes everything after the xpath_expression optional, I've left it has mandatory simply to avoid lots of rework of the function (would need new null checks, memory handling would need reworking). So if you don't specify the xml_value, what does the xpath_expression get applied to? From what I can gather the xpath_expression would be evalutated against an empty document thereby returning false for every xpath_expression except for 'true()'. Apache Derby has made the xml_value mandatory as well (though I'll stress my conclusion wasn't based on this fact). If you think it would better to adhere more closely to the standard I can certainly look to do so. From a cursory glance at libxml's API I think it should be straight forward to query against an empty document such that I wouldn't need ot code for the exceptional case (or cases if I've missed others). Regards, -- Mike Fowler Registered Linux user: 379787 -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers