Merge pull request #347 from DataDog/dd/vtable

Add Go API for virtual tables

Author: mattn

_example/vtable/main.go

@@ -0,0 +1,37 @@
+package main
+
+import (
+	"database/sql"
+	"fmt"
+	"github.com/mattn/go-sqlite3"
+	"log"
+)
+
+func main() {
+	sql.Register("sqlite3_with_extensions", &sqlite3.SQLiteDriver{
+		ConnectHook: func(conn *sqlite3.SQLiteConn) error {
+			return conn.CreateModule("github", githubModule{})
+		},
+	})
+	db, err := sql.Open("sqlite3_with_extensions", ":memory:")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer db.Close()
+
+	_, err = db.Exec("create virtual table repo using github(id, full_name, description, html_url)")
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	rows, err := db.Query("select id, full_name, description, html_url from repo")
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer rows.Close()
+	for rows.Next() {
+		var id, full_name, description, html_url string
+		rows.Scan(&id, &full_name, &description, &html_url)
+		fmt.Printf("%s: %s\n\t%s\n\t%s\n\n", id, full_name, description, html_url)
+	}
+}

_example/vtable/vtable.go

@@ -0,0 +1,110 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"github.com/DataDog/go-sqlite3"
+	"io/ioutil"
+	"net/http"
+)
+
+type GithubRepo struct {
+	ID          int    `json:"id"`
+	FullName    string `json:"full_name"`
+	Description string `json:"description"`
+	HtmlURL     string `json:"html_url"`
+}
+
+type githubModule struct {
+}
+
+func (m githubModule) Create(c *sqlite3.SQLiteConn, args []string) (sqlite3.VTab, error) {
+	err := c.DeclareVTab(fmt.Sprintf(`
+		CREATE TABLE %s (
+			id INT,
+			full_name TEXT,
+			description TEXT,
+			html_url TEXT
+		)`, args[0]))
+	if err != nil {
+		return nil, err
+	}
+	return &ghRepoTable{}, nil
+}
+
+func (m githubModule) Connect(c *sqlite3.SQLiteConn, args []string) (sqlite3.VTab, error) {
+	return m.Create(c, args)
+}
+
+func (m githubModule) DestroyModule() {}
+
+type ghRepoTable struct {
+	repos []GithubRepo
+}
+
+func (v *ghRepoTable) Open() (sqlite3.VTabCursor, error) {
+	resp, err := http.Get("https://api.github.com/repositories")
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	body, err := ioutil.ReadAll(resp.Body)
+	if err != nil {
+		return nil, err
+	}
+
+	repos := make([]GithubRepo, 0)
+	if err := json.Unmarshal(body, &repos); err != nil {
+		return nil, err
+	}
+	return &ghRepoCursor{0, repos}, nil
+}
+
+func (v *ghRepoTable) BestIndex(cst []sqlite3.InfoConstraint, ob []sqlite3.InfoOrderBy) (*sqlite3.IndexResult, error) {
+	return &sqlite3.IndexResult{}, nil
+}
+
+func (v *ghRepoTable) Disconnect() error { return nil }
+func (v *ghRepoTable) Destroy() error    { return nil }
+
+type ghRepoCursor struct {
+	index int
+	repos []GithubRepo
+}
+
+func (vc *ghRepoCursor) Column(c *sqlite3.SQLiteContext, col int) error {
+	switch col {
+	case 0:
+		c.ResultInt(vc.repos[vc.index].ID)
+	case 1:
+		c.ResultText(vc.repos[vc.index].FullName)
+	case 2:
+		c.ResultText(vc.repos[vc.index].Description)
+	case 3:
+		c.ResultText(vc.repos[vc.index].HtmlURL)
+	}
+	return nil
+}
+
+func (vc *ghRepoCursor) Filter(idxNum int, idxStr string, vals []interface{}) error {
+	vc.index = 0
+	return nil
+}
+
+func (vc *ghRepoCursor) Next() error {
+	vc.index++
+	return nil
+}
+
+func (vc *ghRepoCursor) EOF() bool {
+	return vc.index >= len(vc.repos)
+}
+
+func (vc *ghRepoCursor) Rowid() (int64, error) {
+	return int64(vc.index), nil
+}
+
+func (vc *ghRepoCursor) Close() error {
+	return nil
+}

sqlite3.go

@@ -627,11 +627,11 @@ func (d *SQLiteDriver) Open(dsn string) (driver.Conn, error) {
 
 // Close the connection.
 func (c *SQLiteConn) Close() error {
-	deleteHandles(c)
 	rv := C.sqlite3_close_v2(c.db)
 	if rv != C.SQLITE_OK {
 		return c.lastError()
 	}
+	deleteHandles(c)
 	c.db = nil
 	runtime.SetFinalizer(c, nil)
 	return nil

sqlite_context.go

@@ -0,0 +1,103 @@
+// Copyright (C) 2014 Yasuhiro Matsumoto <[email protected]>.
+//
+// Use of this source code is governed by an MIT-style
+// license that can be found in the LICENSE file.
+
+package sqlite3
+
+/*
+
+#ifndef USE_LIBSQLITE3
+#include <sqlite3-binding.h>
+#else
+#include <sqlite3.h>
+#endif
+#include <stdlib.h>
+// These wrappers are necessary because SQLITE_TRANSIENT
+// is a pointer constant, and cgo doesn't translate them correctly.
+
+static inline void my_result_text(sqlite3_context *ctx, char *p, int np) {
+	sqlite3_result_text(ctx, p, np, SQLITE_TRANSIENT);
+}
+
+static inline void my_result_blob(sqlite3_context *ctx, void *p, int np) {
+	sqlite3_result_blob(ctx, p, np, SQLITE_TRANSIENT);
+}
+*/
+import "C"
+
+import (
+	"math"
+	"reflect"
+	"unsafe"
+)
+
+const i64 = unsafe.Sizeof(int(0)) > 4
+
+type ZeroBlobLength int32
+type SQLiteContext C.sqlite3_context
+
+// ResultBool sets the result of an SQL function.
+func (c *SQLiteContext) ResultBool(b bool) {
+	if b {
+		c.ResultInt(1)
+	} else {
+		c.ResultInt(0)
+	}
+}
+
+// ResultBlob sets the result of an SQL function.
+// See: sqlite3_result_blob, http://sqlite.org/c3ref/result_blob.html
+func (c *SQLiteContext) ResultBlob(b []byte) {
+	if i64 && len(b) > math.MaxInt32 {
+		C.sqlite3_result_error_toobig((*C.sqlite3_context)(c))
+		return
+	}
+	var p *byte
+	if len(b) > 0 {
+		p = &b[0]
+	}
+	C.my_result_blob((*C.sqlite3_context)(c), unsafe.Pointer(p), C.int(len(b)))
+}
+
+// ResultDouble sets the result of an SQL function.
+// See: sqlite3_result_double, http://sqlite.org/c3ref/result_blob.html
+func (c *SQLiteContext) ResultDouble(d float64) {
+	C.sqlite3_result_double((*C.sqlite3_context)(c), C.double(d))
+}
+
+// ResultInt sets the result of an SQL function.
+// See: sqlite3_result_int, http://sqlite.org/c3ref/result_blob.html
+func (c *SQLiteContext) ResultInt(i int) {
+	if i64 && (i > math.MaxInt32 || i < math.MinInt32) {
+		C.sqlite3_result_int64((*C.sqlite3_context)(c), C.sqlite3_int64(i))
+	} else {
+		C.sqlite3_result_int((*C.sqlite3_context)(c), C.int(i))
+	}
+}
+
+// ResultInt64 sets the result of an SQL function.
+// See: sqlite3_result_int64, http://sqlite.org/c3ref/result_blob.html
+func (c *SQLiteContext) ResultInt64(i int64) {
+	C.sqlite3_result_int64((*C.sqlite3_context)(c), C.sqlite3_int64(i))
+}
+
+// ResultNull sets the result of an SQL function.
+// See: sqlite3_result_null, http://sqlite.org/c3ref/result_blob.html
+func (c *SQLiteContext) ResultNull() {
+	C.sqlite3_result_null((*C.sqlite3_context)(c))
+}
+
+// ResultText sets the result of an SQL function.
+// See: sqlite3_result_text, http://sqlite.org/c3ref/result_blob.html
+func (c *SQLiteContext) ResultText(s string) {
+	h := (*reflect.StringHeader)(unsafe.Pointer(&s))
+	cs, l := (*C.char)(unsafe.Pointer(h.Data)), C.int(h.Len)
+	C.my_result_text((*C.sqlite3_context)(c), cs, l)
+}
+
+// ResultZeroblob sets the result of an SQL function.
+// See: sqlite3_result_zeroblob, http://sqlite.org/c3ref/result_blob.html
+func (c *SQLiteContext) ResultZeroblob(n ZeroBlobLength) {
+	C.sqlite3_result_zeroblob((*C.sqlite3_context)(c), C.int(n))
+}