mirror of https://github.com/tstack/lnav
[sqlite] include generate_series() extension
Timothy Stack
3 years ago
parent
92fd72aa97
commit
6f4791ec35
@ -0,0 +1,448 @@
|
||||
/*
|
||||
** 2015-08-18
|
||||
**
|
||||
** 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 similar results to the eponymous function in PostgreSQL.
|
||||
** Examples:
|
||||
**
|
||||
** SELECT * FROM generate_series(0,100,5);
|
||||
**
|
||||
** The query above returns integers from 0 through 100 counting by steps
|
||||
** of 5.
|
||||
**
|
||||
** SELECT * FROM generate_series(0,100);
|
||||
**
|
||||
** Integers from 0 through 100 with a step size of 1.
|
||||
**
|
||||
** SELECT * FROM generate_series(20) LIMIT 10;
|
||||
**
|
||||
** Integers 20 through 29.
|
||||
**
|
||||
** 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
|
||||
** );
|
||||
**
|
||||
** 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.
|
||||
*/
|
||||
#include "sqlite3ext.h"
|
||||
SQLITE_EXTENSION_INIT1
|
||||
#include <assert.h>
|
||||
#include <string.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
|
||||
*/
|
||||
typedef struct series_cursor series_cursor;
|
||||
struct series_cursor {
|
||||
sqlite3_vtab_cursor base; /* Base class - must be first */
|
||||
int isDesc; /* True to count down rather than up */
|
||||
sqlite3_int64 iRowid; /* The rowid */
|
||||
sqlite3_int64 iValue; /* Current value ("value") */
|
||||
sqlite3_int64 mnValue; /* Mimimum value ("start") */
|
||||
sqlite3_int64 mxValue; /* Maximum value ("stop") */
|
||||
sqlite3_int64 iStep; /* Increment ("step") */
|
||||
};
|
||||
|
||||
/*
|
||||
** 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_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));
|
||||
#ifdef SQLITE_VTAB_INNOCUOUS
|
||||
sqlite3_vtab_config(db, SQLITE_VTAB_INNOCUOUS);
|
||||
#endif
|
||||
}
|
||||
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->isDesc ){
|
||||
pCur->iValue -= pCur->iStep;
|
||||
}else{
|
||||
pCur->iValue += pCur->iStep;
|
||||
}
|
||||
pCur->iRowid++;
|
||||
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->mnValue; break;
|
||||
case SERIES_COLUMN_STOP: x = pCur->mxValue; break;
|
||||
case SERIES_COLUMN_STEP: x = pCur->iStep; break;
|
||||
default: x = pCur->iValue; break;
|
||||
}
|
||||
sqlite3_result_int64(ctx, x);
|
||||
return SQLITE_OK;
|
||||
}
|
||||
|
||||
/*
|
||||
** Return the rowid for the current row. In this implementation, the
|
||||
** first row returned is assigned rowid value 1, and each subsequent
|
||||
** row a value 1 more than that of the previous.
|
||||
*/
|
||||
static int seriesRowid(sqlite3_vtab_cursor *cur, sqlite_int64 *pRowid){
|
||||
series_cursor *pCur = (series_cursor*)cur;
|
||||
*pRowid = pCur->iRowid;
|
||||
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;
|
||||
if( pCur->isDesc ){
|
||||
return pCur->iValue < pCur->mnValue;
|
||||
}else{
|
||||
return pCur->iValue > pCur->mxValue;
|
||||
}
|
||||
}
|
||||
|
||||
/* 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
|
||||
|
||||
/*
|
||||
** 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:
|
||||
**
|
||||
** 1: start=VALUE
|
||||
** 2: stop=VALUE
|
||||
** 4: step=VALUE
|
||||
**
|
||||
** Also, if bit 8 is set, that means that the series should be output
|
||||
** in descending order rather than in ascending order. If bit 16 is
|
||||
** set, then output must appear in ascending order.
|
||||
**
|
||||
** 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 i = 0;
|
||||
(void)idxStrUnused;
|
||||
if( idxNum & 1 ){
|
||||
pCur->mnValue = sqlite3_value_int64(argv[i++]);
|
||||
}else{
|
||||
pCur->mnValue = 0;
|
||||
}
|
||||
if( idxNum & 2 ){
|
||||
pCur->mxValue = sqlite3_value_int64(argv[i++]);
|
||||
}else{
|
||||
pCur->mxValue = 0xffffffff;
|
||||
}
|
||||
if( idxNum & 4 ){
|
||||
pCur->iStep = sqlite3_value_int64(argv[i++]);
|
||||
if( pCur->iStep==0 ){
|
||||
pCur->iStep = 1;
|
||||
}else if( pCur->iStep<0 ){
|
||||
pCur->iStep = -pCur->iStep;
|
||||
if( (idxNum & 16)==0 ) idxNum |= 8;
|
||||
}
|
||||
}else{
|
||||
pCur->iStep = 1;
|
||||
}
|
||||
for(i=0; i<argc; i++){
|
||||
if( sqlite3_value_type(argv[i])==SQLITE_NULL ){
|
||||
/* If any of the constraints have a NULL value, then return no rows.
|
||||
** See ticket https://www.sqlite.org/src/info/fac496b61722daf2 */
|
||||
pCur->mnValue = 1;
|
||||
pCur->mxValue = 0;
|
||||
break;
|
||||
}
|
||||
}
|
||||
if( idxNum & 8 ){
|
||||
pCur->isDesc = 1;
|
||||
pCur->iValue = pCur->mxValue;
|
||||
if( pCur->iStep>0 ){
|
||||
pCur->iValue -= (pCur->mxValue - pCur->mnValue)%pCur->iStep;
|
||||
}
|
||||
}else{
|
||||
pCur->isDesc = 0;
|
||||
pCur->iValue = pCur->mnValue;
|
||||
}
|
||||
pCur->iRowid = 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:
|
||||
**
|
||||
** (1) start = $value -- constraint exists
|
||||
** (2) stop = $value -- constraint exists
|
||||
** (4) step = $value -- constraint exists
|
||||
** (8) output in descending order
|
||||
*/
|
||||
static int seriesBestIndex(
|
||||
sqlite3_vtab *vtab,
|
||||
sqlite3_index_info *pIdxInfo
|
||||
){
|
||||
int i, j; /* Loop over constraints */
|
||||
int idxNum = 0; /* The query plan bitmask */
|
||||
int unusableMask = 0; /* Mask of unusable constraints */
|
||||
int nArg = 0; /* Number of arguments that seriesFilter() expects */
|
||||
int aIdx[3]; /* Constraints on start, stop, and step */
|
||||
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] = -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 */
|
||||
if( pConstraint->iColumn<SERIES_COLUMN_START ) continue;
|
||||
iCol = pConstraint->iColumn - SERIES_COLUMN_START;
|
||||
assert( iCol>=0 && iCol<=2 );
|
||||
iMask = 1 << iCol;
|
||||
if( pConstraint->usable==0 ){
|
||||
unusableMask |= iMask;
|
||||
continue;
|
||||
}else if( pConstraint->op==SQLITE_INDEX_CONSTRAINT_EQ ){
|
||||
idxNum |= iMask;
|
||||
aIdx[iCol] = i;
|
||||
}
|
||||
}
|
||||
for(i=0; i<3; i++){
|
||||
if( (j = aIdx[i])>=0 ){
|
||||
pIdxInfo->aConstraintUsage[j].argvIndex = ++nArg;
|
||||
pIdxInfo->aConstraintUsage[j].omit = !SQLITE_SERIES_CONSTRAINT_VERIFY;
|
||||
}
|
||||
}
|
||||
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 & 3)==3 ){
|
||||
/* 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 ){
|
||||
if( pIdxInfo->aOrderBy[0].desc ){
|
||||
idxNum |= 8;
|
||||
}else{
|
||||
idxNum |= 16;
|
||||
}
|
||||
pIdxInfo->orderByConsumed = 1;
|
||||
}
|
||||
}else{
|
||||
if (!(idxNum & 1)) {
|
||||
vtab->zErrMsg = sqlite3_mprintf("the start parameter is required");
|
||||
} else {
|
||||
vtab->zErrMsg = sqlite3_mprintf("the stop parameter is required");
|
||||
}
|
||||
return SQLITE_ERROR;
|
||||
}
|
||||
pIdxInfo->idxNum = idxNum;
|
||||
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 */
|
||||
};
|
||||
|
||||
#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 = 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;
|
||||
}
|
||||
Loading…
Reference in New Issue