refactor: replace per-dialect extractors with generic extractor

Collapse the mssql- and postgres-specific extractors into a single generic implementation driven by the DB dialect interface.

internal/app/db-wrapper/postgres.go

@@ -3,14 +3,17 @@ package dbwrapper
 import (
 	"context"
 	"errors"
+	"fmt"
+	"strings"
 
+	dbdialects "git.ksdemosapps.com/kylesoda/go-migrate/internal/app/db-wrapper/db_dialects"
 	"github.com/jackc/pgx/v5"
 	"github.com/jackc/pgx/v5/pgxpool"
 )
 
 func init() {
-	Register("postgres", func() DbWrapper {
-		return &postgresDbWrapper{dialect: "postgres"}
+	Register(dbdialects.Postgres, func() DbWrapper {
+		return &postgresDbWrapper{dialect: dbdialects.Postgres}
 	})
 }
 
@@ -126,3 +129,75 @@ func (pw *postgresDbWrapper) SaveMassive(ctx context.Context, schema string, tab
 
 	return affectedRows, nil
 }
+
+func (pw *postgresDbWrapper) QueryFromObject(ctx context.Context, q ExtractionQuery) (RowsResult, error) {
+	var sbQuery strings.Builder
+
+	sbQuery.WriteString("SELECT ")
+
+	if len(q.columns) == 0 {
+		sbQuery.WriteString("*")
+	} else {
+		for i, col := range q.columns {
+			switch col.Type() {
+			case "GEOMETRY":
+				fmt.Fprintf(&sbQuery, `ST_AsEWKB("%s") AS "%s"`, col.Name(), col.Name())
+			default:
+				fmt.Fprintf(&sbQuery, `"%s"`, col.Name())
+			}
+
+			if i < len(q.columns)-1 {
+				sbQuery.WriteString(", ")
+			}
+		}
+	}
+
+	fmt.Fprintf(&sbQuery, ` FROM "%s"."%s"`, q.Schema, q.Table)
+
+	if q.LowerLimit.IsValid || q.UpperLimit.IsValid {
+		sbQuery.WriteString(" WHERE ")
+		paramIdx := 1
+
+		if q.LowerLimit.IsValid {
+			fmt.Fprintf(&sbQuery, `"%s"`, q.PrimaryKey)
+			if q.LowerLimit.IsInclusive {
+				sbQuery.WriteString(" >=")
+			} else {
+				sbQuery.WriteString(" >")
+			}
+			fmt.Fprintf(&sbQuery, " $%d", paramIdx)
+			paramIdx++
+		}
+
+		if q.LowerLimit.IsValid && q.UpperLimit.IsValid {
+			sbQuery.WriteString(" AND ")
+		}
+
+		if q.UpperLimit.IsValid {
+			fmt.Fprintf(&sbQuery, `"%s"`, q.PrimaryKey)
+			if q.UpperLimit.IsInclusive {
+				sbQuery.WriteString(" <=")
+			} else {
+				sbQuery.WriteString(" <")
+			}
+			fmt.Fprintf(&sbQuery, " $%d", paramIdx)
+			paramIdx++
+		}
+	}
+
+	fmt.Fprintf(&sbQuery, ` ORDER BY "%s" ASC`, q.PrimaryKey)
+
+	queryString := sbQuery.String()
+
+	var queryArgs []any
+
+	if q.LowerLimit.IsValid {
+		queryArgs = append(queryArgs, q.LowerLimit.Value)
+	}
+
+	if q.UpperLimit.IsValid {
+		queryArgs = append(queryArgs, q.UpperLimit.Value)
+	}
+
+	return pw.Query(ctx, queryString, queryArgs...)
+}