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reading_timestamp.go
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/
reading_timestamp.go
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package examples_lib
import (
"fmt"
"os"
"time"
tiledb "github.com/TileDB-Inc/TileDB-Go"
)
// Name of array.
var timestampArrayName = "timestamp_metadata"
func createTimestampArray() {
// Create a TileDB context.
ctx, err := tiledb.NewContext(nil)
checkError(err)
defer ctx.Free()
// The array will be 4x4 with dimensions "rows" and "cols", with domain [1,4].
domain, err := tiledb.NewDomain(ctx)
checkError(err)
defer domain.Free()
rowDim, err := tiledb.NewDimension(ctx, "rows", []int32{1, 4}, int32(4))
checkError(err)
defer rowDim.Free()
colDim, err := tiledb.NewDimension(ctx, "cols", []int32{1, 4}, int32(4))
checkError(err)
defer colDim.Free()
err = domain.AddDimensions(rowDim, colDim)
checkError(err)
// The array will be dense.
schema, err := tiledb.NewArraySchema(ctx, tiledb.TILEDB_DENSE)
checkError(err)
defer schema.Free()
err = schema.SetDomain(domain)
checkError(err)
err = schema.SetCellOrder(tiledb.TILEDB_ROW_MAJOR)
checkError(err)
err = schema.SetTileOrder(tiledb.TILEDB_ROW_MAJOR)
checkError(err)
// Add a single attribute "a" so each (i,j) cell can store an integer.
a, err := tiledb.NewAttribute(ctx, "a", tiledb.TILEDB_INT32)
checkError(err)
defer a.Free()
err = schema.AddAttributes(a)
checkError(err)
// Create the (empty) array on disk.
array, err := tiledb.NewArray(ctx, timestampArrayName)
checkError(err)
defer array.Free()
err = array.Create(schema)
checkError(err)
}
func writeTimestampArray(key string, value string, timestamp uint64, bias int32) {
ctx, err := tiledb.NewContext(nil)
checkError(err)
defer ctx.Free()
// Prepare some data for the array
data := []int32{
1, 2 + bias, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16}
// Open the array for writing and create the query.
array, err := tiledb.NewArray(ctx, timestampArrayName)
checkError(err)
defer array.Free()
err = array.OpenAt(tiledb.TILEDB_WRITE, timestamp)
checkError(err)
defer array.Close()
query, err := tiledb.NewQuery(ctx, array)
checkError(err)
defer query.Free()
err = query.SetLayout(tiledb.TILEDB_ROW_MAJOR)
checkError(err)
_, err = query.SetBuffer("a", data)
checkError(err)
// Perform the write and close the array.
err = query.Submit()
checkError(err)
fmt.Printf("Writing %s: %s\n", key, value)
err = array.PutMetadata(key, value)
checkError(err)
err = query.Finalize()
checkError(err)
}
func writeTimestampArrayMeta(key string, value string, timestamp uint64) {
ctx, err := tiledb.NewContext(nil)
checkError(err)
defer ctx.Free()
// Open the array for writing
array, err := tiledb.NewArray(ctx, timestampArrayName)
checkError(err)
defer array.Free()
err = array.OpenAt(tiledb.TILEDB_WRITE, timestamp)
checkError(err)
defer array.Close()
fmt.Printf("Writing %s: %s\n", key, value)
err = array.PutMetadata(key, value)
checkError(err)
}
func readTimestampArray(timestamp uint64) {
ctx, err := tiledb.NewContext(nil)
checkError(err)
defer ctx.Free()
// Prepare the array for reading
array, err := tiledb.NewArray(ctx, timestampArrayName)
checkError(err)
defer array.Free()
err = array.OpenAt(tiledb.TILEDB_READ, timestamp)
checkError(err)
defer array.Close()
// Slice only rows 1, 2 and cols 2, 3, 4
subArray := []int32{1, 2, 2, 4}
// Prepare the vector that will hold the result (of size 6 elements)
data := make([]int32, 6)
// Prepare the query
query, err := tiledb.NewQuery(ctx, array)
checkError(err)
defer query.Free()
err = query.SetSubArray(subArray)
checkError(err)
err = query.SetLayout(tiledb.TILEDB_ROW_MAJOR)
checkError(err)
_, err = query.SetBuffer("a", data)
checkError(err)
// Submit the query and close the array.
err = query.Submit()
checkError(err)
_, _, value, err := array.GetMetadata("meta_key")
checkError(err)
// String can be retrieved:
fmt.Printf("Value: %v\n", value.(string))
err = query.Finalize()
checkError(err)
// Print out the results.
fmt.Println(data)
}
func getTimestamp() uint64 {
return uint64(time.Now().UTC().UnixNano() / 1000000)
}
// RunTimestampArray shows timestamp correlation of written data and metadata
func RunTimestampArray() {
createTimestampArray()
// Write data and metadata
t1 := getTimestamp()
writeTimestampArray("meta_key", "Write1", t1, 0)
time.Sleep(2000 * time.Millisecond)
// Write metadata only
t2 := getTimestamp()
writeTimestampArrayMeta("meta_key", "Write2", t2)
time.Sleep(2000 * time.Millisecond)
// Write metadata only
t3 := getTimestamp()
writeTimestampArrayMeta("meta_key", "Write3", t3)
readTimestampArray(t1)
readTimestampArray(t2)
readTimestampArray(t3)
if _, err := os.Stat(timestampArrayName); err == nil {
err = os.RemoveAll(timestampArrayName)
checkError(err)
}
// Writing data and metadata
createTimestampArray()
t1 = getTimestamp()
writeTimestampArray("meta_key", "Write1", t1, 0)
time.Sleep(2000 * time.Millisecond)
t2 = getTimestamp()
writeTimestampArray("meta_key", "Write2", t2, 1)
time.Sleep(2000 * time.Millisecond)
t3 = getTimestamp()
writeTimestampArray("meta_key", "Write3", t3, 2)
readTimestampArray(t1)
readTimestampArray(t2)
readTimestampArray(t3)
// Cleanup example so unit tests are clean
if _, err := os.Stat(timestampArrayName); err == nil {
err = os.RemoveAll(timestampArrayName)
checkError(err)
}
}