add pager support to sql shell

go/cmd/dolt/commands/blame.go

@@ -130,7 +130,7 @@ func (cmd BlameCmd) Exec(ctx context.Context, commandStr string, args []string,
 		return 1
 	}
 
-	err = engine.PrettyPrintResults(sqlCtx, engine.FormatTabular, schema, ri)
+	err = engine.PrettyPrintResults(sqlCtx, engine.FormatTabular, schema, ri, false)
 	if err != nil {
 		iohelp.WriteLine(cli.CliOut, err.Error())
 		return 1

go/cmd/dolt/commands/cvcmds/verify_constraints.go

@@ -179,7 +179,7 @@ func printViolationsForTable(ctx context.Context, dbName, tblName string, tbl *d
 
 	limitItr := &sqlLimitIter{itr: sqlItr, limit: 50}
 
-	err = engine.PrettyPrintResults(sCtx, engine.FormatTabular, sqlSch, limitItr)
+	err = engine.PrettyPrintResults(sCtx, engine.FormatTabular, sqlSch, limitItr, false)
 	if err != nil {
 		return errhand.BuildDError("Error outputting rows").AddCause(err).Build()
 	}

go/cmd/dolt/commands/engine/sql_print.go

@@ -33,6 +33,7 @@ import (
 	"github.com/dolthub/dolt/go/libraries/doltcore/table/untyped/csv"
 	"github.com/dolthub/dolt/go/libraries/doltcore/table/untyped/tabular"
 	"github.com/dolthub/dolt/go/libraries/utils/iohelp"
+	"github.com/dolthub/dolt/go/store/util/outputpager"
 )
 
 type PrintResultFormat byte
@@ -54,16 +55,16 @@ const (
 )
 
 // PrettyPrintResults prints the result of a query in the format provided
-func PrettyPrintResults(ctx *sql.Context, resultFormat PrintResultFormat, sqlSch sql.Schema, rowIter sql.RowIter) (rerr error) {
-	return prettyPrintResultsWithSummary(ctx, resultFormat, sqlSch, rowIter, PrintNoSummary)
+func PrettyPrintResults(ctx *sql.Context, resultFormat PrintResultFormat, sqlSch sql.Schema, rowIter sql.RowIter, pageResults bool) (rerr error) {
+	return prettyPrintResultsWithSummary(ctx, resultFormat, sqlSch, rowIter, PrintNoSummary, pageResults)
 }
 
 // PrettyPrintResultsExtended prints the result of a query in the format provided, including row count and timing info
-func PrettyPrintResultsExtended(ctx *sql.Context, resultFormat PrintResultFormat, sqlSch sql.Schema, rowIter sql.RowIter) (rerr error) {
-	return prettyPrintResultsWithSummary(ctx, resultFormat, sqlSch, rowIter, PrintRowCountAndTiming)
+func PrettyPrintResultsExtended(ctx *sql.Context, resultFormat PrintResultFormat, sqlSch sql.Schema, rowIter sql.RowIter, pageResults bool) (rerr error) {
+	return prettyPrintResultsWithSummary(ctx, resultFormat, sqlSch, rowIter, PrintRowCountAndTiming, pageResults)
 }
 
-func prettyPrintResultsWithSummary(ctx *sql.Context, resultFormat PrintResultFormat, sqlSch sql.Schema, rowIter sql.RowIter, summary PrintSummaryBehavior) (rerr error) {
+func prettyPrintResultsWithSummary(ctx *sql.Context, resultFormat PrintResultFormat, sqlSch sql.Schema, rowIter sql.RowIter, summary PrintSummaryBehavior, pageResults bool) (rerr error) {
 	defer func() {
 		closeErr := rowIter.Close(ctx)
 		if rerr == nil && closeErr != nil {
@@ -79,35 +80,55 @@ func prettyPrintResultsWithSummary(ctx *sql.Context, resultFormat PrintResultFor
 	}
 
 	var wr table.SqlRowWriter
-
-	switch resultFormat {
-	case FormatCsv:
-		var err error
-		wr, err = csv.NewCSVSqlWriter(iohelp.NopWrCloser(cli.CliOut), sqlSch, csv.NewCSVInfo())
-		if err != nil {
-			return err
+	var err error
+	var numRows int
+
+	// Function to print results. A function is required because we need to wrap the whole process in a swap of
+	// IO streams. This is done with cli.ExecuteWithStdioRestored, which requires a resultless function. As
+	// a result, we need to depend on side effects to numRows and err to determine if it was successful.
+	printEm := func() {
+		writerStream := cli.CliOut
+		if pageResults {
+			pager := outputpager.Start()
+			defer pager.Stop()
+			writerStream = pager.Writer
 		}
-	case FormatJson:
-		var err error
-		wr, err = json.NewJSONSqlWriter(iohelp.NopWrCloser(cli.CliOut), sqlSch)
-		if err != nil {
-			return err
-		}
-	case FormatTabular:
-		wr = tabular.NewFixedWidthTableWriter(sqlSch, iohelp.NopWrCloser(cli.CliOut), 100)
-	case FormatNull:
-		wr = nullWriter{}
-	case FormatVertical:
-		wr = newVerticalRowWriter(iohelp.NopWrCloser(cli.CliOut), sqlSch)
-	case FormatParquet:
-		var err error
-		wr, err = parquet.NewParquetRowWriter(sqlSch, iohelp.NopWrCloser(cli.CliOut))
-		if err != nil {
-			return err
+
+		switch resultFormat {
+		case FormatCsv:
+			var err error
+			wr, err = csv.NewCSVSqlWriter(iohelp.NopWrCloser(writerStream), sqlSch, csv.NewCSVInfo())
+			if err != nil {
+				return
+			}
+		case FormatJson:
+			var err error
+			wr, err = json.NewJSONSqlWriter(iohelp.NopWrCloser(writerStream), sqlSch)
+			if err != nil {
+				return
+			}
+		case FormatTabular:
+			wr = tabular.NewFixedWidthTableWriter(sqlSch, iohelp.NopWrCloser(writerStream), 100)
+		case FormatNull:
+			wr = nullWriter{}
+		case FormatVertical:
+			wr = newVerticalRowWriter(iohelp.NopWrCloser(writerStream), sqlSch)
+		case FormatParquet:
+			var err error
+			wr, err = parquet.NewParquetRowWriter(sqlSch, iohelp.NopWrCloser(writerStream))
+			if err != nil {
+				return
+			}
 		}
+
+		numRows, err = writeResultSet(ctx, rowIter, wr)
 	}
 
-	numRows, err := writeResultSet(ctx, rowIter, wr)
+	if pageResults {
+		cli.ExecuteWithStdioRestored(printEm)
+	} else {
+		printEm()
+	}
 	if err != nil {
 		return err
 	}

go/cmd/dolt/commands/schcmds/tags.go

@@ -140,7 +140,7 @@ func (cmd TagsCmd) Exec(ctx context.Context, commandStr string, args []string, d
 	}
 
 	sqlCtx := sql.NewContext(ctx)
-	err = engine.PrettyPrintResults(sqlCtx, outputFmt, headerSchema, sql.RowsToRowIter(rows...))
+	err = engine.PrettyPrintResults(sqlCtx, outputFmt, headerSchema, sql.RowsToRowIter(rows...), false)
 
 	return commands.HandleVErrAndExitCode(errhand.VerboseErrorFromError(err), usage)
 }

go/cmd/dolt/commands/sql.go

@@ -356,7 +356,7 @@ func listSavedQueries(ctx *sql.Context, qryist cli.Queryist, dEnv *env.DoltEnv,
 	}
 
 	query := "SELECT * FROM " + doltdb.DoltQueryCatalogTableName
-	return sqlHandleVErrAndExitCode(qryist, execQuery(ctx, qryist, query, format), usage)
+	return sqlHandleVErrAndExitCode(qryist, execSingleQuery(ctx, qryist, query, format), usage)
 }
 
 func executeSavedQuery(ctx *sql.Context, qryist cli.Queryist, dEnv *env.DoltEnv, savedQueryName string, format engine.PrintResultFormat, usage cli.UsagePrinter) int {
@@ -376,7 +376,7 @@ func executeSavedQuery(ctx *sql.Context, qryist cli.Queryist, dEnv *env.DoltEnv,
 	}
 
 	cli.PrintErrf("Executing saved query '%s':\n%s\n", savedQueryName, sq.Query)
-	return sqlHandleVErrAndExitCode(qryist, execQuery(ctx, qryist, sq.Query, format), usage)
+	return sqlHandleVErrAndExitCode(qryist, execSingleQuery(ctx, qryist, sq.Query, format), usage)
 }
 
 func queryMode(
@@ -406,7 +406,7 @@ func execSaveQuery(ctx *sql.Context, dEnv *env.DoltEnv, qryist cli.Queryist, apr
 
 	saveName := apr.GetValueOrDefault(saveFlag, "")
 
-	verr := execQuery(ctx, qryist, query, format)
+	verr := execSingleQuery(ctx, qryist, query, format)
 	if verr != nil {
 		return sqlHandleVErrAndExitCode(qryist, verr, usage)
 	}
@@ -430,7 +430,9 @@ func execSaveQuery(ctx *sql.Context, dEnv *env.DoltEnv, qryist cli.Queryist, apr
 	return 0
 }
 
-func execQuery(
+// execSingleQuery runs a single query and prints the results. This is not intended for use in interactive modes, especially
+// the shell.
+func execSingleQuery(
 	sqlCtx *sql.Context,
 	qryist cli.Queryist,
 	query string,
@@ -443,7 +445,7 @@ func execQuery(
 	}
 
 	if rowIter != nil {
-		err = engine.PrettyPrintResults(sqlCtx, format, sqlSch, rowIter)
+		err = engine.PrettyPrintResults(sqlCtx, format, sqlSch, rowIter, false)
 		if err != nil {
 			return errhand.VerboseErrorFromError(err)
 		}
@@ -659,7 +661,7 @@ func execBatchMode(ctx *sql.Context, qryist cli.Queryist, input io.Reader, conti
 					fileReadProg.printNewLineIfNeeded()
 				}
 			}
-			err = engine.PrettyPrintResults(ctx, format, sqlSch, rowIter)
+			err = engine.PrettyPrintResults(ctx, format, sqlSch, rowIter, false)
 			if err != nil {
 				err = buildBatchSqlErr(scanner.state.statementStartLine, query, err)
 				if !continueOnErr {
@@ -749,6 +751,7 @@ func execShell(sqlCtx *sql.Context, qryist cli.Queryist, format engine.PrintResu
 
 	initialCtx := sqlCtx.Context
 
+	pagerEnabled := false
 	// Used for the \edit command.
 	lastSqlCmd := ""
 
@@ -787,9 +790,18 @@ func execShell(sqlCtx *sql.Context, qryist cli.Queryist, format engine.PrintResu
 			}
 
 			if cmdType == DoltCliCommand {
-				err := handleSlashCommand(sqlCtx, subCmd, query, cliCtx)
-				if err != nil {
-					shell.Println(color.RedString(err.Error()))
+				if _, ok := subCmd.(SlashPager); ok {
+					p, err := handlePagerCommand(query)
+					if err != nil {
+						shell.Println(color.RedString(err.Error()))
+					} else {
+						pagerEnabled = p
+					}
+				} else {
+					err := handleSlashCommand(sqlCtx, subCmd, query, cliCtx)
+					if err != nil {
+						shell.Println(color.RedString(err.Error()))
+					}
 				}
 			} else {
 				if cmdType == TransformCommand {
@@ -805,9 +817,9 @@ func execShell(sqlCtx *sql.Context, qryist cli.Queryist, format engine.PrintResu
 				} else if rowIter != nil {
 					switch closureFormat {
 					case engine.FormatTabular, engine.FormatVertical:
-						err = engine.PrettyPrintResultsExtended(sqlCtx, closureFormat, sqlSch, rowIter)
+						err = engine.PrettyPrintResultsExtended(sqlCtx, closureFormat, sqlSch, rowIter, pagerEnabled)
 					default:
-						err = engine.PrettyPrintResults(sqlCtx, closureFormat, sqlSch, rowIter)
+						err = engine.PrettyPrintResults(sqlCtx, closureFormat, sqlSch, rowIter, pagerEnabled)
 					}
 
 					if err != nil {

go/cmd/dolt/commands/sql_slash.go

@@ -40,6 +40,7 @@ var slashCmds = []cli.Command{
 	MergeCmd{},
 	SlashHelp{},
 	SlashEdit{},
+	SlashPager{},
 }
 
 // parseSlashCmd parses a command line string into a slice of strings, splitting on spaces, but allowing spaces within
@@ -215,3 +216,53 @@ func (s SlashEdit) ArgParser() *argparser.ArgParser {
 	// No arguments.
 	return &argparser.ArgParser{}
 }
+
+type SlashPager struct{}
+
+func (s SlashPager) Docs() *cli.CommandDocumentation {
+	//TODO
+	return &cli.CommandDocumentation{}
+}
+
+func (s SlashPager) ArgParser() *argparser.ArgParser {
+	return &argparser.ArgParser{}
+}
+
+var _ cli.Command = SlashPager{}
+
+func (s SlashPager) Name() string {
+	return "pager"
+}
+func (s SlashPager) Description() string {
+	return "Enable or Disable the result pager"
+}
+
+// Exec is a little special because the shell is interested in the response. So rather than call Exec, it calls
+// handlePagerCommand function.
+func (s SlashPager) Exec(ctx context.Context, commandStr string, args []string, dEnv *env.DoltEnv, cliCtx cli.CliContext) int {
+	panic("runtime error. SlashPager.Exec should never be called.")
+}
+
+// handlePagerCommand executes the pager command and returns true if pager should be on, or false otherwise. An error
+// could come up if they provided weird input.
+func handlePagerCommand(fullCmd string) (bool, error) {
+	tokens := strings.Split(fullCmd, " ")
+
+	if len(tokens) == 0 || tokens[0] != "\\pager" {
+		return false, fmt.Errorf("runtime error: Expected \\pager command.")
+	}
+
+	if len(tokens) == 1 {
+		return false, fmt.Errorf("Usage: \\pager [on|off]")
+	}
+
+	// Kind of sloppy here,`\pager foo bar on` will work, but not the end of the world.
+	if tokens[len(tokens)-1] == "on" {
+		return true, nil
+	}
+	if tokens[len(tokens)-1] == "off" {
+		return false, nil
+	}
+
+	return false, fmt.Errorf("Usage: \\pager [on|off]")
+}