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https://github.com/mariadb-corporation/mariadb-columnstore-engine.git
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183 lines
6.2 KiB
C++
183 lines
6.2 KiB
C++
/* Copyright (C) 2017 MariaDB Corporation
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License
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as published by the Free Software Foundation; version 2 of
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the License.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
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MA 02110-1301, USA. */
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/***********************************************************************
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* $Id$
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*
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* mcsv1_UDAF.h
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***********************************************************************/
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/**
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* Columnstore interface for writing a User Defined Aggregate
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* Functions (UDAF) and User Defined Analytic Functions (UDAnF)
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* or a function that can act as either - UDA(n)F
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*
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* The basic steps are:
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*
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* 1. Create a the UDA(n)F function interface in some .h file.
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* 2. Create the UDF function implementation in some .cpp file
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* 3. Create the connector stub (MariaDB UDAF definition) for
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* this UDF function.
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* 4. build the dynamic library using all of the source.
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* 5 Put the library in $COLUMNSTORE_INSTALL/lib of
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* all modules
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* 6. restart the Columnstore system.
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* 7. notify mysqld about the new functions with commands like:
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*
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* CREATE AGGREGATE FUNCTION allnull returns BOOL soname
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* 'libudf_mysql.so';
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*
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*/
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#pragma once
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#include <cstdlib>
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#include <string>
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#include <vector>
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#include <tr1/unordered_map>
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#include "mcsv1_udaf.h"
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#include "calpontsystemcatalog.h"
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#include "windowfunctioncolumn.h"
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#define EXPORT
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namespace mcsv1sdk
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{
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// Override mcsv1_UDAF to build your User Defined Aggregate (UDAF) and/or
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// User Defined Analytic Function (UDAnF).
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// These will be singleton classes, so don't put any instance
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// specific data in here. All instance data is stored in mcsv1Context
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// passed to each user function and retrieved by the getUserData() method.
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//
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// Each API function returns a ReturnCode. If ERROR is returned at any time,
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// the query is aborted, getInterrupted() will begin to return true and the
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// message set in config->setErrorMessage() is returned to MariaDB.
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class allnull : public mcsv1_UDAF
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{
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public:
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// Defaults OK
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allnull() : mcsv1_UDAF(){};
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~allnull() override = default;
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/**
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* init()
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*
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* Mandatory. Implement this to initialize flags and instance
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* data. Called once per SQL statement. You can do any sanity
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* checks here.
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*
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* colTypes (in) - A vector of ColDataType defining the
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* parameters of the UDA(n)F call. These can be used to decide
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* to override the default return type. If desired, the new
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* return type can be set by context->setReturnType() and
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* decimal precision can be set in context->
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* setResultDecimalCharacteristics.
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*
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* Return mcsv1_UDAF::ERROR on any error, such as non-compatible
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* colTypes or wrong number of arguments. Else return
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* mcsv1_UDAF::SUCCESS.
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*/
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ReturnCode init(mcsv1Context* context, ColumnDatum* colTypes) override;
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/**
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* reset()
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*
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* Mandatory. Reset the UDA(n)F for a new group, partition or,
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* in some cases, new Window Frame. Do not free any memory
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* allocated by context->setUserDataSize(). The SDK Framework owns
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* that memory and will handle that. Use this opportunity to
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* reset any variables in context->getUserData() needed for the
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* next aggregation. May be called multiple times if running in
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* a ditributed fashion.
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*
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* Use this opportunity to initialize the userData.
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*/
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ReturnCode reset(mcsv1Context* context) override;
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/**
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* nextValue()
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*
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* Mandatory. Handle a single row.
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*
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* colsIn - A vector of data structure describing the input
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* data.
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*
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* This function is called once for every row in the filtered
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* result set (before aggregation). It is very important that
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* this function is efficient.
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*
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* If the UDAF is running in a distributed fashion, nextValue
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* cannot depend on order, as it will only be called for each
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* row found on the specific PM.
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*
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* valsIn (in) - a vector of the parameters from the row.
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*/
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ReturnCode nextValue(mcsv1Context* context, ColumnDatum* valsIn) override;
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/**
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* subEvaluate()
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*
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* Mandatory -- Called if the UDAF is running in a distributed
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* fashion. Columnstore tries to run all aggregate functions
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* distributed, depending on context.
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*
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* Perform an aggregation on rows partially aggregated by
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* nextValue. Columnstore calls nextValue for each row on a
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* given PM for a group (GROUP BY). subEvaluate is called on the
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* UM to consolodate those values into a single instance of
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* userData. Keep your aggregated totals in context's userData.
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* The first time this is called for a group, reset() would have
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* been called with this version of userData.
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*
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* Called for every partial data set in each group in GROUP BY.
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*
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* When subEvaluate has been called for all subAggregated data
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* sets, Evaluate will be called with the same context as here.
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*
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* valIn (In) - This is a pointer to a memory block of the size
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* set in setUserDataSize. It will contain the value of userData
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* as seen in the last call to NextValue for a given PM.
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*
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*/
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ReturnCode subEvaluate(mcsv1Context* context, const UserData* userDataIn) override;
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/**
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* evaluate()
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*
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* Mandatory. Get the aggregated value.
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*
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* Called for every new group if UDAF GROUP BY, UDAnF partition
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* or, in some cases, new Window Frame.
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*
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* Set the aggregated value into valOut. The datatype is assumed
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* to be the same as that set in the init() function;
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*
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* If the UDAF is running in a distributed fashion, evaluate is
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* called after a series of subEvaluate calls.
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*
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* valOut (out) - Set the aggregated value here. The datatype is
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* assumed to be the same as that set in the init() function;
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*
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* To return a NULL value, don't assign to valOut.
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*/
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ReturnCode evaluate(mcsv1Context* context, static_any::any& valOut) override;
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};
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} // namespace mcsv1sdk
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#undef EXPORT
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