ClickHouse/src/Parsers/ASTProjectionDeclaration.h

#pragma once

#include <Parsers/IAST.h>


namespace DB
{
/** name (subquery)
  */
class ASTProjectionDeclaration : public IAST
{
public:
    String name;
    IAST * query;

    /** Get the text that identifies this element. */
    String getID(char) const override { return "Projection"; }

    ASTPtr clone() const override;
    void formatImpl(const FormatSettings & s, FormatState & state, FormatStateStacked frame) const override;
};

}
Projections TODO (suggested by Nikolai) 1. Build query plan fro current query (inside storage::read) up to WithMergableState 2. Check, that plan is simple enough: Aggregating - Expression - Filter - ReadFromStorage (or simplier) 3. Check, that filter is the same as filter in projection, and also expression calculates the same aggregation keys as in projection 4. Return WithMergableState if projection applies 3 will be easier to do with ActionsDAG, cause it sees all functions, and dependencies are direct (but it is possible with ExpressionActions also) Also need to figure out how prewhere works for projections, and row_filter_policies. wip 2021-02-10 14:12:49 +00:00			`#pragma once`

			`#include <Parsers/IAST.h>`


			`namespace DB`
			`{`
			`/** name (subquery)`
			`*/`
			`class ASTProjectionDeclaration : public IAST`
			`{`
			`public:`
			`String name;`
Implement antlr parser for projections (#24245) * implement projection grammer for antlr parser * Add comment 2021-06-02 15:09:55 +00:00			`IAST * query;`
Projections TODO (suggested by Nikolai) 1. Build query plan fro current query (inside storage::read) up to WithMergableState 2. Check, that plan is simple enough: Aggregating - Expression - Filter - ReadFromStorage (or simplier) 3. Check, that filter is the same as filter in projection, and also expression calculates the same aggregation keys as in projection 4. Return WithMergableState if projection applies 3 will be easier to do with ActionsDAG, cause it sees all functions, and dependencies are direct (but it is possible with ExpressionActions also) Also need to figure out how prewhere works for projections, and row_filter_policies. wip 2021-02-10 14:12:49 +00:00
			`/** Get the text that identifies this element. */`
			`String getID(char) const override { return "Projection"; }`

			`ASTPtr clone() const override;`
			`void formatImpl(const FormatSettings & s, FormatState & state, FormatStateStacked frame) const override;`
			`};`

			`}`