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sqlite/ext/misc/series.c
drh e4eaf174a5 Remove an unused variable from the generate_series implementation. 
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/*
** 2015-08-18, 2023-04-28
**
** The author disclaims copyright to this source code. In place of
** a legal notice, here is a blessing:
**
** May you do good and not evil.
** May you find forgiveness for yourself and forgive others.
** May you share freely, never taking more than you give.
**
*************************************************************************
**
** This file demonstrates how to create a table-valued-function using
** a virtual table. This demo implements the generate_series() function
** which gives the same results as the eponymous function in PostgreSQL,
** within the limitation that its arguments are signed 64-bit integers.
**
** Considering its equivalents to generate_series(start,stop,step): A
** value V[n] sequence is produced for integer n ascending from 0 where
** ( V[n] == start + n * step && sgn(V[n] - stop) * sgn(step) >= 0 )
** for each produced value (independent of production time ordering.)
**
** All parameters must be either integer or convertable to integer.
** The start parameter is required.
** The stop parameter defaults to (1<<32)-1 (aka 4294967295 or 0xffffffff)
** The step parameter defaults to 1 and 0 is treated as 1.
**
** Examples:
**
** SELECT * FROM generate_series(0,100,5);
**
** The query above returns integers from 0 through 100 counting by steps
** of 5. In other words, 0, 5, 10, 15, ..., 90, 95, 100. There are a total
** of 21 rows.
**
** SELECT * FROM generate_series(0,100);
**
** Integers from 0 through 100 with a step size of 1. 101 rows.
**
** SELECT * FROM generate_series(20) LIMIT 10;
**
** Integers 20 through 29. 10 rows.
**
** SELECT * FROM generate_series(0,-100,-5);
**
** Integers 0 -5 -10 ... -100. 21 rows.
**
** SELECT * FROM generate_series(0,-1);
**
** Empty sequence.
**
** HOW IT WORKS
**
** The generate_series "function" is really a virtual table with the
** following schema:
**
** CREATE TABLE generate_series(
** value,
** start HIDDEN,
** stop HIDDEN,
** step HIDDEN
** );
**
** The virtual table also has a rowid which is an alias for the value.
**
** Function arguments in queries against this virtual table are translated
** into equality constraints against successive hidden columns. In other
** words, the following pairs of queries are equivalent to each other:
**
** SELECT * FROM generate_series(0,100,5);
** SELECT * FROM generate_series WHERE start=0 AND stop=100 AND step=5;
**
** SELECT * FROM generate_series(0,100);
** SELECT * FROM generate_series WHERE start=0 AND stop=100;
**
** SELECT * FROM generate_series(20) LIMIT 10;
** SELECT * FROM generate_series WHERE start=20 LIMIT 10;
**
** The generate_series virtual table implementation leaves the xCreate method
** set to NULL. This means that it is not possible to do a CREATE VIRTUAL
** TABLE command with "generate_series" as the USING argument. Instead, there
** is a single generate_series virtual table that is always available without
** having to be created first.
**
** The xBestIndex method looks for equality constraints against the hidden
** start, stop, and step columns, and if present, it uses those constraints
** to bound the sequence of generated values. If the equality constraints
** are missing, it uses 0 for start, 4294967295 for stop, and 1 for step.
** xBestIndex returns a small cost when both start and stop are available,
** and a very large cost if either start or stop are unavailable. This
** encourages the query planner to order joins such that the bounds of the
** series are well-defined.
**
** Update on 2024-08-22:
** xBestIndex now also looks for equality and inequality constraints against
** the value column and uses those constraints as additional bounds against
** the sequence range. Thus, a query like this:
**
** SELECT value FROM generate_series($SA,$EA)
** WHERE value BETWEEN $SB AND $EB;
**
** Is logically the same as:
**
** SELECT value FROM generate_series(max($SA,$SB),min($EA,$EB));
**
** Constraints on the value column can server as substitutes for constraints
** on the hidden start and stop columns. So, the following two queries
** are equivalent:
**
** SELECT value FROM generate_series($S,$E);
** SELECT value FROM generate_series WHERE value BETWEEN $S and $E;
**
*/
#include "sqlite3ext.h"
SQLITE_EXTENSION_INIT1
#include <assert.h>
#include <string.h>
#include <limits.h>
#include <math.h>
#ifndef SQLITE_OMIT_VIRTUALTABLE
/* series_cursor is a subclass of sqlite3_vtab_cursor which will
** serve as the underlying representation of a cursor that scans
** over rows of the result.
**
** iOBase, iOTerm, and iOStep are the original values of the
** start=, stop=, and step= constraints on the query. These are
** the values reported by the start, stop, and step columns of the
** virtual table.
**
** iBase, iTerm, iStep, and bDescp are the actual values used to generate
** the sequence. These might be different from the iOxxxx values.
** For example in
**
** SELECT value FROM generate_series(1,11,2)
** WHERE value BETWEEN 4 AND 8;
**
** The iOBase is 1, but the iBase is 5. iOTerm is 11 but iTerm is 7.
** Another example:
**
** SELECT value FROM generate_series(1,15,3) ORDER BY value DESC;
**
** The cursor initialization for the above query is:
**
** iOBase = 1 iBase = 13
** iOTerm = 15 iTerm = 1
** iOStep = 3 iStep = 3 bDesc = 1
**
** The actual step size is unsigned so that can have a value of
** +9223372036854775808 which is needed for querys like this:
**
** SELECT value
** FROM generate_series(9223372036854775807,
** -9223372036854775808,
** -9223372036854775808)
** ORDER BY value ASC;
**
** The setup for the previous query will be:
**
** iOBase = 9223372036854775807 iBase = -1
** iOTerm = -9223372036854775808 iTerm = 9223372036854775807
** iOStep = -9223372036854775808 iStep = 9223372036854775808 bDesc = 0
*/
typedef unsigned char u8;
typedef struct series_cursor series_cursor;
struct series_cursor {
sqlite3_vtab_cursor base; /* Base class - must be first */
sqlite3_int64 iOBase; /* Original starting value ("start") */
sqlite3_int64 iOTerm; /* Original terminal value ("stop") */
sqlite3_int64 iOStep; /* Original step value */
sqlite3_int64 iBase; /* Starting value to actually use */
sqlite3_int64 iTerm; /* Terminal value to actually use */
sqlite3_uint64 iStep; /* The step size */
sqlite3_int64 iValue; /* Current value */
u8 bDesc; /* iStep is really negative */
u8 bDone; /* True if stepped past last element */
};
/*
** Computed the difference between two 64-bit signed integers using a
** convoluted computation designed to work around the silly restriction
** against signed integer overflow in C.
*/
static sqlite3_uint64 span64(sqlite3_int64 a, sqlite3_int64 b){
assert( a>=b );
return (*(sqlite3_uint64*)&a) - (*(sqlite3_uint64*)&b);
}
/*
** Add or substract an unsigned 64-bit integer from a signed 64-bit integer
** and return the new signed 64-bit integer.
*/
static sqlite3_int64 add64(sqlite3_int64 a, sqlite3_uint64 b){
sqlite3_uint64 x = *(sqlite3_uint64*)&a;
x += b;
return *(sqlite3_int64*)&x;
}
static sqlite3_int64 sub64(sqlite3_int64 a, sqlite3_uint64 b){
sqlite3_uint64 x = *(sqlite3_uint64*)&a;
x -= b;
return *(sqlite3_int64*)&x;
}
/*
** The seriesConnect() method is invoked to create a new
** series_vtab that describes the generate_series virtual table.
**
** Think of this routine as the constructor for series_vtab objects.
**
** All this routine needs to do is:
**
** (1) Allocate the series_vtab object and initialize all fields.
**
** (2) Tell SQLite (via the sqlite3_declare_vtab() interface) what the
** result set of queries against generate_series will look like.
*/
static int seriesConnect(
sqlite3 *db,
void *pUnused,
int argcUnused, const char *const*argvUnused,
sqlite3_vtab **ppVtab,
char **pzErrUnused
){
sqlite3_vtab *pNew;
int rc;
/* Column numbers */
#define SERIES_COLUMN_ROWID (-1)
#define SERIES_COLUMN_VALUE 0
#define SERIES_COLUMN_START 1
#define SERIES_COLUMN_STOP 2
#define SERIES_COLUMN_STEP 3
(void)pUnused;
(void)argcUnused;
(void)argvUnused;
(void)pzErrUnused;
rc = sqlite3_declare_vtab(db,
"CREATE TABLE x(value,start hidden,stop hidden,step hidden)");
if( rc==SQLITE_OK ){
pNew = *ppVtab = sqlite3_malloc( sizeof(*pNew) );
if( pNew==0 ) return SQLITE_NOMEM;
memset(pNew, 0, sizeof(*pNew));
sqlite3_vtab_config(db, SQLITE_VTAB_INNOCUOUS);
}
return rc;
}
/*
** This method is the destructor for series_cursor objects.
*/
static int seriesDisconnect(sqlite3_vtab *pVtab){
sqlite3_free(pVtab);
return SQLITE_OK;
}
/*
** Constructor for a new series_cursor object.
*/
static int seriesOpen(sqlite3_vtab *pUnused, sqlite3_vtab_cursor **ppCursor){
series_cursor *pCur;
(void)pUnused;
pCur = sqlite3_malloc( sizeof(*pCur) );
if( pCur==0 ) return SQLITE_NOMEM;
memset(pCur, 0, sizeof(*pCur));
*ppCursor = &pCur->base;
return SQLITE_OK;
}
/*
** Destructor for a series_cursor.
*/
static int seriesClose(sqlite3_vtab_cursor *cur){
sqlite3_free(cur);
return SQLITE_OK;
}
/*
** Advance a series_cursor to its next row of output.
*/
static int seriesNext(sqlite3_vtab_cursor *cur){
series_cursor *pCur = (series_cursor*)cur;
if( pCur->iValue==pCur->iTerm ){
pCur->bDone = 1;
}else if( pCur->bDesc ){
pCur->iValue = sub64(pCur->iValue, pCur->iStep);
assert( pCur->iValue>=pCur->iTerm );
}else{
pCur->iValue = add64(pCur->iValue, pCur->iStep);
assert( pCur->iValue<=pCur->iTerm );
}
return SQLITE_OK;
}
/*
** Return values of columns for the row at which the series_cursor
** is currently pointing.
*/
static int seriesColumn(
sqlite3_vtab_cursor *cur, /* The cursor */
sqlite3_context *ctx, /* First argument to sqlite3_result_...() */
int i /* Which column to return */
){
series_cursor *pCur = (series_cursor*)cur;
sqlite3_int64 x = 0;
switch( i ){
case SERIES_COLUMN_START: x = pCur->iOBase; break;
case SERIES_COLUMN_STOP: x = pCur->iOTerm; break;
case SERIES_COLUMN_STEP: x = pCur->iOStep; break;
default: x = pCur->iValue; break;
}
sqlite3_result_int64(ctx, x);
return SQLITE_OK;
}
#ifndef LARGEST_UINT64
#define LARGEST_INT64 ((sqlite3_int64)0x7fffffffffffffffLL)
#define LARGEST_UINT64 ((sqlite3_uint64)0xffffffffffffffffULL)
#define SMALLEST_INT64 ((sqlite3_int64)0x8000000000000000LL)
#endif
/*
** The rowid is the same as the value.
*/
static int seriesRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
series_cursor *pCur = (series_cursor*)cur;
*pRowid = pCur->iValue;
return SQLITE_OK;
}
/*
** Return TRUE if the cursor has been moved off of the last
** row of output.
*/
static int seriesEof(sqlite3_vtab_cursor *cur){
series_cursor *pCur = (series_cursor*)cur;
return pCur->bDone;
}
/* True to cause run-time checking of the start=, stop=, and/or step=
** parameters. The only reason to do this is for testing the
** constraint checking logic for virtual tables in the SQLite core.
*/
#ifndef SQLITE_SERIES_CONSTRAINT_VERIFY
# define SQLITE_SERIES_CONSTRAINT_VERIFY 0
#endif
/*
** Return the number of steps between pCur->iBase and pCur->iTerm if
** the step width is pCur->iStep.
*/
static sqlite3_uint64 seriesSteps(series_cursor *pCur){
if( pCur->bDesc ){
assert( pCur->iBase >= pCur->iTerm );
return span64(pCur->iBase, pCur->iTerm)/pCur->iStep;
}else{
assert( pCur->iBase <= pCur->iTerm );
return span64(pCur->iTerm, pCur->iBase)/pCur->iStep;
}
}
#if defined(SQLITE_ENABLE_MATH_FUNCTIONS) || defined(_WIN32)
/*
** Case 1 (the most common case):
** The standard math library is available so use ceil() and floor() from there.
*/
static double seriesCeil(double r){ return ceil(r); }
static double seriesFloor(double r){ return floor(r); }
#elif defined(__GNUC__) && !defined(SQLITE_DISABLE_INTRINSIC)
/*
** Case 2 (2nd most common): Use GCC/Clang builtins
*/
static double seriesCeil(double r){ return __builtin_ceil(r); }
static double seriesFloor(double r){ return __builtin_floor(r); }
#else
/*
** Case 3 (rarely happens): Use home-grown ceil() and floor() routines.
*/
static double seriesCeil(double r){
sqlite3_int64 x;
if( r!=r ) return r;
if( r<=(-4503599627370496.0) ) return r;
if( r>=(+4503599627370496.0) ) return r;
x = (sqlite3_int64)r;
if( r==(double)x ) return r;
if( r>(double)x ) x++;
return (double)x;
}
static double seriesFloor(double r){
sqlite3_int64 x;
if( r!=r ) return r;
if( r<=(-4503599627370496.0) ) return r;
if( r>=(+4503599627370496.0) ) return r;
x = (sqlite3_int64)r;
if( r==(double)x ) return r;
if( r<(double)x ) x--;
return (double)x;
}
#endif
/*
** This method is called to "rewind" the series_cursor object back
** to the first row of output. This method is always called at least
** once prior to any call to seriesColumn() or seriesRowid() or
** seriesEof().
**
** The query plan selected by seriesBestIndex is passed in the idxNum
** parameter. (idxStr is not used in this implementation.) idxNum
** is a bitmask showing which constraints are available:
**
** 0x0001: start=VALUE
** 0x0002: stop=VALUE
** 0x0004: step=VALUE
** 0x0008: descending order
** 0x0010: ascending order
** 0x0020: LIMIT VALUE
** 0x0040: OFFSET VALUE
** 0x0080: value=VALUE
** 0x0100: value>=VALUE
** 0x0200: value>VALUE
** 0x1000: value<=VALUE
** 0x2000: value<VALUE
**
** This routine should initialize the cursor and position it so that it
** is pointing at the first row, or pointing off the end of the table
** (so that seriesEof() will return true) if the table is empty.
*/
static int seriesFilter(
sqlite3_vtab_cursor *pVtabCursor,
int idxNum, const char *idxStrUnused,
int argc, sqlite3_value **argv
){
series_cursor *pCur = (series_cursor *)pVtabCursor;
int iArg = 0; /* Arguments used so far */
int i; /* Loop counter */
sqlite3_int64 iMin = SMALLEST_INT64; /* Smallest allowed output value */
sqlite3_int64 iMax = LARGEST_INT64; /* Largest allowed output value */
sqlite3_int64 iLimit = 0; /* if >0, the value of the LIMIT */
sqlite3_int64 iOffset = 0; /* if >0, the value of the OFFSET */
(void)idxStrUnused;
/* If any constraints have a NULL value, then return no rows.
** See ticket https://sqlite.org/src/info/fac496b61722daf2
*/
for(i=0; i<argc; i++){
if( sqlite3_value_type(argv[i])==SQLITE_NULL ){
goto series_no_rows;
}
}
/* Capture the three HIDDEN parameters to the virtual table and insert
** default values for any parameters that are omitted.
*/
if( idxNum & 0x01 ){
pCur->iOBase = sqlite3_value_int64(argv[iArg++]);
}else{
pCur->iOBase = 0;
}
if( idxNum & 0x02 ){
pCur->iOTerm = sqlite3_value_int64(argv[iArg++]);
}else{
pCur->iOTerm = 0xffffffff;
}
if( idxNum & 0x04 ){
pCur->iOStep = sqlite3_value_int64(argv[iArg++]);
if( pCur->iOStep==0 ) pCur->iOStep = 1;
}else{
pCur->iOStep = 1;
}
/* If there are constraints on the value column but there are
** no constraints on the start, stop, and step columns, then
** initialize the default range to be the entire range of 64-bit signed
** integers. This range will contracted by the value column constraints
** further below.
*/
if( (idxNum & 0x05)==0 && (idxNum & 0x0380)!=0 ){
pCur->iOBase = SMALLEST_INT64;
}
if( (idxNum & 0x06)==0 && (idxNum & 0x3080)!=0 ){
pCur->iOTerm = LARGEST_INT64;
}
pCur->iBase = pCur->iOBase;
pCur->iTerm = pCur->iOTerm;
if( pCur->iOStep>0 ){
pCur->iStep = pCur->iOStep;
}else if( pCur->iOStep>SMALLEST_INT64 ){
pCur->iStep = -pCur->iOStep;
}else{
pCur->iStep = LARGEST_INT64;
pCur->iStep++;
}
pCur->bDesc = pCur->iOStep<0;
if( pCur->bDesc==0 && pCur->iBase>pCur->iTerm ){
goto series_no_rows;
}
if( pCur->bDesc!=0 && pCur->iBase<pCur->iTerm ){
goto series_no_rows;
}
/* Extract the LIMIT and OFFSET values, but do not apply them yet.
** The range must first be constrained by the limits on value.
*/
if( idxNum & 0x20 ){
iLimit = sqlite3_value_int64(argv[iArg++]);
if( idxNum & 0x40 ){
iOffset = sqlite3_value_int64(argv[iArg++]);
}
}
/* Narrow the range of iMin and iMax (the minimum and maximum outputs)
** based on equality and inequality constraints on the "value" column.
*/
if( idxNum & 0x3380 ){
if( idxNum & 0x0080 ){ /* value=X */
if( sqlite3_value_numeric_type(argv[iArg])==SQLITE_FLOAT ){
double r = sqlite3_value_double(argv[iArg++]);
if( r==seriesCeil(r)
&& r>=(double)SMALLEST_INT64
&& r<=(double)LARGEST_INT64
){
iMin = iMax = (sqlite3_int64)r;
}else{
goto series_no_rows;
}
}else{
iMin = iMax = sqlite3_value_int64(argv[iArg++]);
}
}else{
if( idxNum & 0x0300 ){ /* value>X or value>=X */
if( sqlite3_value_numeric_type(argv[iArg])==SQLITE_FLOAT ){
double r = sqlite3_value_double(argv[iArg++]);
if( r<(double)SMALLEST_INT64 ){
iMin = SMALLEST_INT64;
}else if( (idxNum & 0x0200)!=0 && r==seriesCeil(r) ){
iMin = (sqlite3_int64)seriesCeil(r+1.0);
}else{
iMin = (sqlite3_int64)seriesCeil(r);
}
}else{
iMin = sqlite3_value_int64(argv[iArg++]);
if( (idxNum & 0x0200)!=0 ){
if( iMin==LARGEST_INT64 ){
goto series_no_rows;
}else{
iMin++;
}
}
}
}
if( idxNum & 0x3000 ){ /* value<X or value<=X */
if( sqlite3_value_numeric_type(argv[iArg])==SQLITE_FLOAT ){
double r = sqlite3_value_double(argv[iArg++]);
if( r>(double)LARGEST_INT64 ){
iMax = LARGEST_INT64;
}else if( (idxNum & 0x2000)!=0 && r==seriesFloor(r) ){
iMax = (sqlite3_int64)(r-1.0);
}else{
iMax = (sqlite3_int64)seriesFloor(r);
}
}else{
iMax = sqlite3_value_int64(argv[iArg++]);
if( idxNum & 0x2000 ){
if( iMax==SMALLEST_INT64 ){
goto series_no_rows;
}else{
iMax--;
}
}
}
}
if( iMin>iMax ){
goto series_no_rows;
}
}
/* Try to reduce the range of values to be generated based on
** constraints on the "value" column.
*/
if( pCur->bDesc==0 ){
if( pCur->iBase<iMin ){
sqlite3_uint64 span = span64(iMin,pCur->iBase);
pCur->iBase = add64(pCur->iBase, (span/pCur->iStep)*pCur->iStep);
if( pCur->iBase<iMin ){
if( pCur->iBase > sub64(LARGEST_INT64, pCur->iStep) ){
goto series_no_rows;
}
pCur->iBase = add64(pCur->iBase, pCur->iStep);
}
}
if( pCur->iTerm>iMax ){
pCur->iTerm = iMax;
}
}else{
if( pCur->iBase>iMax ){
sqlite3_uint64 span = span64(pCur->iBase,iMax);
pCur->iBase = sub64(pCur->iBase, (span/pCur->iStep)*pCur->iStep);
if( pCur->iBase>iMax ){
if( pCur->iBase < add64(SMALLEST_INT64, pCur->iStep) ){
goto series_no_rows;
}
pCur->iBase = sub64(pCur->iBase, pCur->iStep);
}
}
if( pCur->iTerm<iMin ){
pCur->iTerm = iMin;
}
}
}
/* Adjust iTerm so that it is exactly the last value of the series.
*/
if( pCur->bDesc==0 ){
if( pCur->iBase>pCur->iTerm ){
goto series_no_rows;
}
pCur->iTerm = sub64(pCur->iTerm,
span64(pCur->iTerm,pCur->iBase) % pCur->iStep);
}else{
if( pCur->iBase<pCur->iTerm ){
goto series_no_rows;
}
pCur->iTerm = add64(pCur->iTerm,
span64(pCur->iBase,pCur->iTerm) % pCur->iStep);
}
/* Transform the series generator to output values in the requested
** order.
*/
if( ((idxNum & 0x0008)!=0 && pCur->bDesc==0)
|| ((idxNum & 0x0010)!=0 && pCur->bDesc!=0)
){
sqlite3_int64 tmp = pCur->iBase;
pCur->iBase = pCur->iTerm;
pCur->iTerm = tmp;
pCur->bDesc = !pCur->bDesc;
}
/* Apply LIMIT and OFFSET constraints, if any */
assert( pCur->iStep!=0 );
if( idxNum & 0x20 ){
if( iOffset>0 ){
if( seriesSteps(pCur) < (sqlite3_uint64)iOffset ){
goto series_no_rows;
}else if( pCur->bDesc ){
pCur->iBase = sub64(pCur->iBase, pCur->iStep*iOffset);
}else{
pCur->iBase = add64(pCur->iBase, pCur->iStep*iOffset);
}
}
if( iLimit>=0 && seriesSteps(pCur) > (sqlite3_uint64)iLimit ){
pCur->iTerm = add64(pCur->iBase, (iLimit - 1)*pCur->iStep);
}
}
pCur->iValue = pCur->iBase;
pCur->bDone = 0;
return SQLITE_OK;
series_no_rows:
pCur->iBase = 0;
pCur->iTerm = 0;
pCur->iStep = 1;
pCur->bDesc = 0;
pCur->bDone = 1;
return SQLITE_OK;
}
/*
** SQLite will invoke this method one or more times while planning a query
** that uses the generate_series virtual table. This routine needs to create
** a query plan for each invocation and compute an estimated cost for that
** plan.
**
** In this implementation idxNum is used to represent the
** query plan. idxStr is unused.
**
** The query plan is represented by bits in idxNum:
**
** 0x0001 start = $num
** 0x0002 stop = $num
** 0x0004 step = $num
** 0x0008 output is in descending order
** 0x0010 output is in ascending order
** 0x0020 LIMIT $num
** 0x0040 OFFSET $num
** 0x0080 value = $num
** 0x0100 value >= $num
** 0x0200 value > $num
** 0x1000 value <= $num
** 0x2000 value < $num
**
** Only one of 0x0100 or 0x0200 will be returned. Similarly, only
** one of 0x1000 or 0x2000 will be returned. If the 0x0080 is set, then
** none of the 0xff00 bits will be set.
**
** The order of parameters passed to xFilter is as follows:
**
** * The argument to start= if bit 0x0001 is in the idxNum mask
** * The argument to stop= if bit 0x0002 is in the idxNum mask
** * The argument to step= if bit 0x0004 is in the idxNum mask
** * The argument to LIMIT if bit 0x0020 is in the idxNum mask
** * The argument to OFFSET if bit 0x0040 is in the idxNum mask
** * The argument to value=, or value>= or value> if any of
** bits 0x0380 are in the idxNum mask
** * The argument to value<= or value< if either of bits 0x3000
** are in the mask
**
*/
static int seriesBestIndex(
sqlite3_vtab *pVTab,
sqlite3_index_info *pIdxInfo
){
int i, j; /* Loop over constraints */
int idxNum = 0; /* The query plan bitmask */
#ifndef ZERO_ARGUMENT_GENERATE_SERIES
int bStartSeen = 0; /* EQ constraint seen on the START column */
#endif
int unusableMask = 0; /* Mask of unusable constraints */
int nArg = 0; /* Number of arguments that seriesFilter() expects */
int aIdx[7]; /* Constraints on start, stop, step, LIMIT, OFFSET,
** and value. aIdx[5] covers value=, value>=, and
** value>, aIdx[6] covers value<= and value< */
const struct sqlite3_index_constraint *pConstraint;
/* This implementation assumes that the start, stop, and step columns
** are the last three columns in the virtual table. */
assert( SERIES_COLUMN_STOP == SERIES_COLUMN_START+1 );
assert( SERIES_COLUMN_STEP == SERIES_COLUMN_START+2 );
aIdx[0] = aIdx[1] = aIdx[2] = aIdx[3] = aIdx[4] = aIdx[5] = aIdx[6] = -1;
pConstraint = pIdxInfo->aConstraint;
for(i=0; i<pIdxInfo->nConstraint; i++, pConstraint++){
int iCol; /* 0 for start, 1 for stop, 2 for step */
int iMask; /* bitmask for those column */
int op = pConstraint->op;
if( op>=SQLITE_INDEX_CONSTRAINT_LIMIT
&& op<=SQLITE_INDEX_CONSTRAINT_OFFSET
){
if( pConstraint->usable==0 ){
/* do nothing */
}else if( op==SQLITE_INDEX_CONSTRAINT_LIMIT ){
aIdx[3] = i;
idxNum |= 0x20;
}else{
assert( op==SQLITE_INDEX_CONSTRAINT_OFFSET );
aIdx[4] = i;
idxNum |= 0x40;
}
continue;
}
if( pConstraint->iColumn<SERIES_COLUMN_START ){
if( (pConstraint->iColumn==SERIES_COLUMN_VALUE ||
pConstraint->iColumn==SERIES_COLUMN_ROWID)
&& pConstraint->usable
){
switch( op ){
case SQLITE_INDEX_CONSTRAINT_EQ:
case SQLITE_INDEX_CONSTRAINT_IS: {
idxNum |= 0x0080;
idxNum &= ~0x3300;
aIdx[5] = i;
aIdx[6] = -1;
#ifndef ZERO_ARGUMENT_GENERATE_SERIES
bStartSeen = 1;
#endif
break;
}
case SQLITE_INDEX_CONSTRAINT_GE: {
if( idxNum & 0x0080 ) break;
idxNum |= 0x0100;
idxNum &= ~0x0200;
aIdx[5] = i;
#ifndef ZERO_ARGUMENT_GENERATE_SERIES
bStartSeen = 1;
#endif
break;
}
case SQLITE_INDEX_CONSTRAINT_GT: {
if( idxNum & 0x0080 ) break;
idxNum |= 0x0200;
idxNum &= ~0x0100;
aIdx[5] = i;
#ifndef ZERO_ARGUMENT_GENERATE_SERIES
bStartSeen = 1;
#endif
break;
}
case SQLITE_INDEX_CONSTRAINT_LE: {
if( idxNum & 0x0080 ) break;
idxNum |= 0x1000;
idxNum &= ~0x2000;
aIdx[6] = i;
break;
}
case SQLITE_INDEX_CONSTRAINT_LT: {
if( idxNum & 0x0080 ) break;
idxNum |= 0x2000;
idxNum &= ~0x1000;
aIdx[6] = i;
break;
}
}
}
continue;
}
iCol = pConstraint->iColumn - SERIES_COLUMN_START;
assert( iCol>=0 && iCol<=2 );
iMask = 1 << iCol;
#ifndef ZERO_ARGUMENT_GENERATE_SERIES
if( iCol==0 && op==SQLITE_INDEX_CONSTRAINT_EQ ){
bStartSeen = 1;
}
#endif
if( pConstraint->usable==0 ){
unusableMask |= iMask;
continue;
}else if( op==SQLITE_INDEX_CONSTRAINT_EQ ){
idxNum |= iMask;
aIdx[iCol] = i;
}
}
if( aIdx[3]==0 ){
/* Ignore OFFSET if LIMIT is omitted */
idxNum &= ~0x60;
aIdx[4] = 0;
}
for(i=0; i<7; i++){
if( (j = aIdx[i])>=0 ){
pIdxInfo->aConstraintUsage[j].argvIndex = ++nArg;
pIdxInfo->aConstraintUsage[j].omit =
!SQLITE_SERIES_CONSTRAINT_VERIFY || i>=3;
}
}
/* The current generate_column() implementation requires at least one
** argument (the START value). Legacy versions assumed START=0 if the
** first argument was omitted. Compile with -DZERO_ARGUMENT_GENERATE_SERIES
** to obtain the legacy behavior */
#ifndef ZERO_ARGUMENT_GENERATE_SERIES
if( !bStartSeen ){
sqlite3_free(pVTab->zErrMsg);
pVTab->zErrMsg = sqlite3_mprintf(
"first argument to \"generate_series()\" missing or unusable");
return SQLITE_ERROR;
}
#endif
if( (unusableMask & ~idxNum)!=0 ){
/* The start, stop, and step columns are inputs. Therefore if there
** are unusable constraints on any of start, stop, or step then
** this plan is unusable */
return SQLITE_CONSTRAINT;
}
if( (idxNum & 0x03)==0x03 ){
/* Both start= and stop= boundaries are available. This is the
** the preferred case */
pIdxInfo->estimatedCost = (double)(2 - ((idxNum&4)!=0));
pIdxInfo->estimatedRows = 1000;
if( pIdxInfo->nOrderBy>=1 && pIdxInfo->aOrderBy[0].iColumn==0 ){
if( pIdxInfo->aOrderBy[0].desc ){
idxNum |= 0x08;
}else{
idxNum |= 0x10;
}
pIdxInfo->orderByConsumed = 1;
}
}else if( (idxNum & 0x21)==0x21 ){
/* We have start= and LIMIT */
pIdxInfo->estimatedRows = 2500;
}else{
/* If either boundary is missing, we have to generate a huge span
** of numbers. Make this case very expensive so that the query
** planner will work hard to avoid it. */
pIdxInfo->estimatedRows = 2147483647;
}
pIdxInfo->idxNum = idxNum;
#ifdef SQLITE_INDEX_SCAN_HEX
pIdxInfo->idxFlags = SQLITE_INDEX_SCAN_HEX;
#endif
return SQLITE_OK;
}
/*
** This following structure defines all the methods for the
** generate_series virtual table.
*/
static sqlite3_module seriesModule = {
0, /* iVersion */
0, /* xCreate */
seriesConnect, /* xConnect */
seriesBestIndex, /* xBestIndex */
seriesDisconnect, /* xDisconnect */
0, /* xDestroy */
seriesOpen, /* xOpen - open a cursor */
seriesClose, /* xClose - close a cursor */
seriesFilter, /* xFilter - configure scan constraints */
seriesNext, /* xNext - advance a cursor */
seriesEof, /* xEof - check for end of scan */
seriesColumn, /* xColumn - read data */
seriesRowid, /* xRowid - read data */
0, /* xUpdate */
0, /* xBegin */
0, /* xSync */
0, /* xCommit */
0, /* xRollback */
0, /* xFindMethod */
0, /* xRename */
0, /* xSavepoint */
0, /* xRelease */
0, /* xRollbackTo */
0, /* xShadowName */
0 /* xIntegrity */
};
#endif /* SQLITE_OMIT_VIRTUALTABLE */
#ifdef _WIN32
__declspec(dllexport)
#endif
int sqlite3_series_init(
sqlite3 *db,
char **pzErrMsg,
const sqlite3_api_routines *pApi
){
int rc = SQLITE_OK;
SQLITE_EXTENSION_INIT2(pApi);
#ifndef SQLITE_OMIT_VIRTUALTABLE
if( sqlite3_libversion_number()<3008012 && pzErrMsg!=0 ){
*pzErrMsg = sqlite3_mprintf(
"generate_series() requires SQLite 3.8.12 or later");
return SQLITE_ERROR;
}
rc = sqlite3_create_module(db, "generate_series", &seriesModule, 0);
#endif
return rc;
}
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