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Add initial infrastructure for cursors. In where.c, optimize out clauses

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of the form "ORDER BY rowid" if a table scan is being performed.  Do a
reverse table scan if "ORDER BY rowid DESC" is present. (CVS 2141)

FossilOrigin-Name: fc8c1393c86017a816beb52725b68af3b973f979
This commit is contained in:
drh
2004-11-22 19:12:19 +00:00
parent 8237d45ed8
commit b6c29897eb
17 changed files with 671 additions and 93 deletions
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58
src/sqliteInt.h
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@@ -11,7 +11,7 @@
*************************************************************************
** Internal interface definitions for SQLite.
**
** @(#) $Id: sqliteInt.h,v 1.342 2004/11/22 10:02:11 danielk1977 Exp $
** @(#) $Id: sqliteInt.h,v 1.343 2004/11/22 19:12:21 drh Exp $
*/
#ifndef _SQLITEINT_H_
#define _SQLITEINT_H_
@@ -307,6 +307,8 @@ typedef struct AuthContext AuthContext;
typedef struct KeyClass KeyClass;
typedef struct CollSeq CollSeq;
typedef struct KeyInfo KeyInfo;
typedef struct SqlCursor SqlCursor;
typedef struct Fetch Fetch;
/*
** Each database file to be accessed by the system is an instance
@@ -420,7 +422,10 @@ struct sqlite3 {
void *pProgressArg; /* Argument to the progress callback */
int nProgressOps; /* Number of opcodes for progress callback */
#endif
#ifndef SQLITE_OMIT_CURSOR
int nSqlCursor; /* Number of slots in apSqlCursor[] */
SqlCursor **apSqlCursor; /* Pointers to all active SQL cursors */
#endif
int errCode; /* Most recent error code (SQLITE_*) */
u8 enc; /* Text encoding for this database. */
u8 autoCommit; /* The auto-commit flag. */
@@ -429,9 +434,8 @@ struct sqlite3 {
void *pCollNeededArg;
sqlite3_value *pValue; /* Value used for transient conversions */
sqlite3_value *pErr; /* Most recent error message */
char *zErrMsg; /* Most recent error message (UTF-8 encoded) */
char *zErrMsg16; /* Most recent error message (UTF-8 encoded) */
char *zErrMsg16; /* Most recent error message (UTF-16 encoded) */
};
/*
@@ -928,18 +932,20 @@ struct WhereInfo {
WhereLevel a[1]; /* Information about each nest loop in the WHERE */
};
/*
** An instance of the following structure is used to store information
** about a single FETCH sql command.
*/
struct Fetch {
SqlCursor *pCursor; /* Cursor used by the fetch */
int isBackwards; /* Cursor moves backwards if true, forward if false */
int doRewind; /* True to rewind cursor before starting */
};
/*
** An instance of the following structure contains all information
** needed to generate code for a single SELECT statement.
**
** The zSelect field is used when the Select structure must be persistent.
** Normally, the expression tree points to tokens in the original input
** string that encodes the select. But if the Select structure must live
** longer than its input string (for example when it is used to describe
** a VIEW) we have to make a copy of the input string so that the nodes
** of the expression tree will have something to point to. zSelect is used
** to hold that copy.
**
** nLimit is set to -1 if there is no LIMIT clause. nOffset is set to 0.
** If there is a LIMIT clause, the parser sets nLimit to the value of the
** limit and nOffset to the value of the offset (or 0 if there is not
@@ -958,8 +964,8 @@ struct Select {
Select *pPrior; /* Prior select in a compound select statement */
int nLimit, nOffset; /* LIMIT and OFFSET values. -1 means not used */
int iLimit, iOffset; /* Memory registers holding LIMIT & OFFSET counters */
char *zSelect; /* Complete text of the SELECT command */
IdList **ppOpenTemp; /* OP_OpenTemp addresses used by multi-selects */
Fetch *pFetch; /* If this stmt is part of a FETCH command */
};
/*
@@ -1039,6 +1045,11 @@ struct Parse {
u8 explain; /* True if the EXPLAIN flag is found on the query */
u8 useAgg; /* If true, extract field values from the aggregator
** while generating expressions. Normally false */
#ifndef SQLITE_OMIT_CURSOR
u8 fetchDir; /* The direction argument to the FETCH command */
int dirArg1; /* First argument to the direction */
int dirArg2; /* Second argument to the direction */
#endif
int nAgg; /* Number of aggregate expressions */
AggExpr *aAgg; /* An array of aggregate expressions */
Token sErrToken; /* The token at which the error occurred */
@@ -1050,6 +1061,7 @@ struct Parse {
Trigger *pNewTrigger; /* Trigger under construct by a CREATE TRIGGER */
TriggerStack *trigStack; /* Trigger actions being coded */
const char *zAuthContext; /* The 6th parameter to db->xAuth callbacks */
};
/*
@@ -1212,6 +1224,18 @@ typedef struct {
char **pzErrMsg; /* Error message stored here */
} InitData;
/*
** Each SQL cursor (a cursor created by the DECLARE ... CURSOR syntax)
** is represented by an instance of the following structure.
*/
struct SqlCursor {
char *zName; /* Name of this cursor */
int idx; /* Index of this cursor in db->apSqlCursor[] */
Select *pSelect; /* The SELECT statement that defines this cursor */
int nPtr; /* Number of slots in aPtr[] */
sqlite3_value *aPtr; /* Values that define the current cursor position */
};
/*
* This global flag is set for performance testing of triggers. When it is set
@@ -1314,6 +1338,7 @@ void sqlite3SelectUnbind(Select*);
Table *sqlite3SrcListLookup(Parse*, SrcList*);
int sqlite3IsReadOnly(Parse*, Table*, int);
void sqlite3OpenTableForReading(Vdbe*, int iCur, Table*);
void sqlite3OpenTable(Vdbe*, int iCur, Table*, int);
void sqlite3DeleteFrom(Parse*, SrcList*, Expr*);
void sqlite3Update(Parse*, SrcList*, ExprList*, Expr*, int);
WhereInfo *sqlite3WhereBegin(Parse*, SrcList*, Expr*, int, ExprList**);
@@ -1463,4 +1488,11 @@ void sqlite3AlterRenameTable(Parse*, SrcList*, Token*);
int sqlite3GetToken(const unsigned char *, int *);
void sqlite3NestedParse(Parse*, const char*, ...);
#ifndef SQLITE_OMIT_CURSOR
void sqlite3CursorDelete(SqlCursor*);
void sqlite3CursorCreate(Parse*, Token*, Select*);
void sqlite3CursorClose(Parse*, Token*);
void sqlite3Fetch(Parse*, Token*, IdList*);
#endif /* SQLITE_OMIT_CURSOR */
#endif