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WL#962: Added simple, read-only, non-scrolling, asensitive cursors in SPs, using the
(updated) Protocol_cursor class. Also did some bug fixes. Docs/sp-imp-spec.txt: Added CURSOR docs (and fixed typos) Docs/sp-implemented.txt: Updated for CURSORs include/mysqld_error.h: New error codes/messages for CURSORs libmysqld/Makefile.am: SP cursors now needs this. mysql-test/r/sp-error.result: New tests for cursors. mysql-test/r/sp.result: New tests for cursors. mysql-test/t/sp-error.test: New tests for cursors. mysql-test/t/sp.test: New tests for cursors. sql/protocol.cc: We now always have Protocol_cursor (SPs use it) sql/protocol.h: Fixed bugs in Protocol_cursor (for SPs) sql/protocol_cursor.cc: Fixed bugs in Protocol_cursor (for SPs) sql/share/czech/errmsg.txt: New error codes/messages for CURSORs sql/share/danish/errmsg.txt: New error codes/messages for CURSORs sql/share/dutch/errmsg.txt: New error codes/messages for CURSORs sql/share/english/errmsg.txt: New error codes/messages for CURSORs sql/share/estonian/errmsg.txt: New error codes/messages for CURSORs sql/share/french/errmsg.txt: New error codes/messages for CURSORs sql/share/german/errmsg.txt: New error codes/messages for CURSORs sql/share/greek/errmsg.txt: New error codes/messages for CURSORs sql/share/hungarian/errmsg.txt: New error codes/messages for CURSORs sql/share/italian/errmsg.txt: New error codes/messages for CURSORs sql/share/japanese/errmsg.txt: New error codes/messages for CURSORs sql/share/korean/errmsg.txt: New error codes/messages for CURSORs sql/share/norwegian-ny/errmsg.txt: New error codes/messages for CURSORs sql/share/norwegian/errmsg.txt: New error codes/messages for CURSORs sql/share/polish/errmsg.txt: New error codes/messages for CURSORs sql/share/portuguese/errmsg.txt: New error codes/messages for CURSORs sql/share/romanian/errmsg.txt: New error codes/messages for CURSORs sql/share/russian/errmsg.txt: New error codes/messages for CURSORs sql/share/serbian/errmsg.txt: New error codes/messages for CURSORs sql/share/slovak/errmsg.txt: New error codes/messages for CURSORs sql/share/spanish/errmsg.txt: New error codes/messages for CURSORs sql/share/swedish/errmsg.txt: New error codes/messages for CURSORs sql/share/ukrainian/errmsg.txt: New error codes/messages for CURSORs sql/sp_head.cc: Added cursor support. Also fixed problems with item_lists, where pointers and ref_pointer_arrays. sql/sp_head.h: Added cursor support sql/sp_pcontext.cc: Added cursor support sql/sp_pcontext.h: Added cursor support sql/sp_rcontext.cc: Added cursor support, in particular the new sp_cursor class. sql/sp_rcontext.h: Added cursor support, in particular the new sp_cursor class. sql/sql_lex.h: We sometimes need to copy item_lists in LEX when executing substatements in SPs sql/sql_yacc.yy: Added minimal cursor support (not the full syntax yet).
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42 changed files with 1290 additions and 71 deletions
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@ -11,7 +11,7 @@
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which dispatches on the command code (in Lex) to the corresponding code for
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executing that particular query.
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There are thre structures involved in the execution of a query which are of
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There are three structures involved in the execution of a query which are of
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interest to the stored procedure implementation:
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- Lex (mentioned above) is the "compiled" query, that is the output from
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@ -186,7 +186,7 @@
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stored in the table mysql.proc with the name and type as the key, the
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type being one of the enum ("procedure","function").
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A PROCEDURE is just stored int the mysql.proc table. A FUNCTION has an
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A PROCEDURE is just stored in the mysql.proc table. A FUNCTION has an
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additional requirement. They will be called in expressions with the same
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syntax as UDFs, so UDFs and stored FUNCTIONs share the namespace. Thus,
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we must make sure that we do not have UDFs and FUNCTIONs with the same
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@ -293,7 +293,7 @@
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So, stored functions must be handled in a simpilar way, and as a
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consequence, UDFs and functions must not have the same name.
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- Detecting and parsing a FUNCTION invokation
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- Detecting and parsing a FUNCTION invocation
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The existance of UDFs are checked during the lexical analysis (in
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sql_lex.cc:find_keyword()). This has the drawback that they must
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@ -319,7 +319,7 @@
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"on-the-fly" during the execution of *another* statement.
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This makes things a lot more complicated compared to CALL:
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- We can't read and parse the FUNCTION from the mysql.proc table at the
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point of invokation; the server requires that all tables used are
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point of invocation; the server requires that all tables used are
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opened and locked at the beginning of the query execution.
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One "obvious" solution would be to simply push "mysql.proc" to the list
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of tables used by the query, but this implies a "join" with this table
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@ -478,6 +478,67 @@
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7 sp_instr_hpop(2)
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- Cursors
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For stored procedures to be really useful, you want to have cursors.
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MySQL doesn't yet have "real" cursor support (with API and ODBC support,
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allowing updating, arbitrary scrolling, etc), but a simple asensitive,
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non-scrolling, read-only cursor can be implemented in SPs using the
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class Protocol_cursor.
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This class intecepts the creation and sending of results sets and instead
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stores it in-memory, as MYSQL_FIELDS and MYSQL_ROWS (as in the client API).
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To support this, we need the usual name binding support in sp_pcontext
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(similar to variables and conditions) to keep track on declared cursor
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names, and a corresponding run-time mechanism in sp_rcontext.
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Cursors are lexically scoped like everything with a body or BEGIN/END
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block, so they are pushed and poped as usual (see conditions and variables
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above).
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The basic operations on a cursor are OPEN, FETCH and CLOSE, which will
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each have a corresponding instruction. In addition, we need instructions
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to push a new cursor (this will encapsulate the LEX of the SELECT statement
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of the cursor), and a pop instruction:
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- sp_instr_cpush
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Push a cursor to the sp_rcontext. This instruction contains the LEX
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for the select statement
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- sp_instr_cpop
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Pop a number of cursors from the sp_rcontext.
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- sp_instr_copen
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Open a cursor: This will execute the select and get the result set
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in a sepeate memroot.
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- sp_instr_cfetch
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Fetch the next row from the in-memory result set. The instruction
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contains a list of the variables (frame offsets) to set.
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- sp_instr_cclose
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Free the result set.
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A cursor is a separate class, sp_cursor (defined in sp_rcontex.h) which
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encapsulates the basic operations used by the above instructions.
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This class contains the LEX, Protocol_cursor object, and its memroot,
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as well as the cursor's current state.
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Compiling and executing is fairly straight-forward. sp_instr_copen is
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a subclass of sp_instr_stmt and uses its mechanism to execute a
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substatement.
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- Example:
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begin
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declare x int;
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declare c cursor for select a from t1;
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open c;
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fetch c into x;
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close c;
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end
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Pos. Instruction
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0 sp_instr_cpush('select a from ...')
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1 sp_instr_copen(0) # The 0'th cursor
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2 sp_instr_cfetch(0) # Contains the variable list
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3 sp_instr_cclose(0)
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4 sp_instr_cpop(1)
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- Class and function APIs
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This is an outline of the key types. Some types and other details
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in the actual files have been omitted for readability.
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@ -569,6 +630,18 @@
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// Returns the handler count
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uint handlers();
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// Push a cursor
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void push_cursor(LEX_STRING *name);
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// Find a cursor
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my_bool find_cursor(LEX_STRING *name, uint *poff);
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// Pop 'num' cursors
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void pop_cursor(uint num);
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// Return the number of cursors
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uint cursors();
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}
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@ -589,8 +662,9 @@
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class sp_rcontext
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{
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// 'fsize' is the max size of the context, 'hmax' the number of handlers
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sp_rcontext(uint fsize, uint hmax);
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// 'fsize' is the max size of the context, 'hmax' the number of handlers,
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// 'cmax' the number of cursors
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sp_rcontext(uint fsize, uint hmax, , uint cmax);
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// Push value (parameter) 'i' to the frame
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void push_item(Item *i);
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// Restore saved variables from to frame index 'fp' and up.
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void restore_variables(uint fp);
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// Push a cursor for the statement (lex)
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void push_cursor(LEX *lex);
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// Pop 'count' cursors
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void pop_cursors(uint count);
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// Pop all cursors
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void pop_all_cursors();
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// Get the 'i'th cursor
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sp_cursor *get_cursor(uint i);
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}
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@ -709,6 +795,7 @@
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bool suid, char *comment, uint commentlen);
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}
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- Instructions
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- The base class:
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@ -816,6 +903,55 @@
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int execute(THD *thd, uint *nextp);
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}
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- Push a CURSOR
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class sp_instr_cpush : public sp_instr_stmt
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{
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// Push a cursor for statement 'lex'
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sp_instr_cpush(uint ip, LEX *lex)
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int execute(THD *thd, uint *nextp);
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}
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- Pop CURSORs
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class sp_instr_cpop : public sp_instr_stmt
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{
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// Pop 'count' cursors
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sp_instr_cpop(uint ip, uint count)
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int execute(THD *thd, uint *nextp);
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}
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- Open a CURSOR
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class sp_instr_copen : public sp_instr_stmt
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{
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// Open the 'c'th cursor
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sp_instr_copen(uint ip, uint c);
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int execute(THD *thd, uint *nextp);
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}
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- Close a CURSOR
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class sp_instr_cclose : public sp_instr
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{
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// Close the 'c'th cursor
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sp_instr_cclose(uint ip, uint c);
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int execute(THD *thd, uint *nextp);
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}
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- Fetch a row with CURSOR
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class sp_instr_cfetch : public sp_instr
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{
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// Fetch next with the 'c'th cursor
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sp_instr_cfetch(uint ip, uint c);
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int execute(THD *thd, uint *nextp);
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// Add a target variable for the fetch
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void add_to_varlist(struct sp_pvar *var);
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}
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- Utility functions: sp.h
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#define SP_OK 0
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- Access control
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- Routine characteristics (mostly used for external languages)
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- SQL-99 COMMIT (related to BEGIN/END)
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- DECLARE CURSOR ...
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- FOR-loops (as it requires cursors)
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- FOR-loops
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- CASCADE/RESTRICT for ALTER and DROP
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- ALTER/DROP METHOD (as it implies User Defined Types)
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- SIGNAL and RESIGNAL, and UNDO handlers
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- "Non-query" FUNCTIONs only
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- Prepared SP caching
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- CONDITIONs and HANDLERs
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- Simple read-only CURSORs.
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List of what's implemented:
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The semantics of CONDITIONs is expanded to allow catching MySQL error
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codes as well. UNDO handlers are not implemented (since we don't have
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SQL-99 style transaction control yet).
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- Simple read-only CURSORs are implemented, but not yet any of the
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optional arguments to DECLARE (SCROLL, SENSITIVE, etc) or FETCH
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(NEXT, PRIOR, etc). Cursors are ASENSITIVE, READ-ONLY, non-SCROLLing.
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(The additional syntax will be added for completeness, but for the
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most part unsupported with the current underlying cursor mechanism.)
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Closed questions:
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